- •About the Author
- •About the Technical Editor
- •Credits
- •Is This Book for You?
- •Software Versions
- •Conventions This Book Uses
- •What the Icons Mean
- •How This Book Is Organized
- •How to Use This Book
- •What’s on the Companion CD
- •What Is Excel Good For?
- •What’s New in Excel 2010?
- •Moving around a Worksheet
- •Introducing the Ribbon
- •Using Shortcut Menus
- •Customizing Your Quick Access Toolbar
- •Working with Dialog Boxes
- •Using the Task Pane
- •Creating Your First Excel Worksheet
- •Entering Text and Values into Your Worksheets
- •Entering Dates and Times into Your Worksheets
- •Modifying Cell Contents
- •Applying Number Formatting
- •Controlling the Worksheet View
- •Working with Rows and Columns
- •Understanding Cells and Ranges
- •Copying or Moving Ranges
- •Using Names to Work with Ranges
- •Adding Comments to Cells
- •What Is a Table?
- •Creating a Table
- •Changing the Look of a Table
- •Working with Tables
- •Getting to Know the Formatting Tools
- •Changing Text Alignment
- •Using Colors and Shading
- •Adding Borders and Lines
- •Adding a Background Image to a Worksheet
- •Using Named Styles for Easier Formatting
- •Understanding Document Themes
- •Creating a New Workbook
- •Opening an Existing Workbook
- •Saving a Workbook
- •Using AutoRecover
- •Specifying a Password
- •Organizing Your Files
- •Other Workbook Info Options
- •Closing Workbooks
- •Safeguarding Your Work
- •Excel File Compatibility
- •Exploring Excel Templates
- •Understanding Custom Excel Templates
- •Printing with One Click
- •Changing Your Page View
- •Adjusting Common Page Setup Settings
- •Adding a Header or Footer to Your Reports
- •Copying Page Setup Settings across Sheets
- •Preventing Certain Cells from Being Printed
- •Preventing Objects from Being Printed
- •Creating Custom Views of Your Worksheet
- •Understanding Formula Basics
- •Entering Formulas into Your Worksheets
- •Editing Formulas
- •Using Cell References in Formulas
- •Using Formulas in Tables
- •Correcting Common Formula Errors
- •Using Advanced Naming Techniques
- •Tips for Working with Formulas
- •A Few Words about Text
- •Text Functions
- •Advanced Text Formulas
- •Date-Related Worksheet Functions
- •Time-Related Functions
- •Basic Counting Formulas
- •Advanced Counting Formulas
- •Summing Formulas
- •Conditional Sums Using a Single Criterion
- •Conditional Sums Using Multiple Criteria
- •Introducing Lookup Formulas
- •Functions Relevant to Lookups
- •Basic Lookup Formulas
- •Specialized Lookup Formulas
- •The Time Value of Money
- •Loan Calculations
- •Investment Calculations
- •Depreciation Calculations
- •Understanding Array Formulas
- •Understanding the Dimensions of an Array
- •Naming Array Constants
- •Working with Array Formulas
- •Using Multicell Array Formulas
- •Using Single-Cell Array Formulas
- •Working with Multicell Array Formulas
- •What Is a Chart?
- •Understanding How Excel Handles Charts
- •Creating a Chart
- •Working with Charts
- •Understanding Chart Types
- •Learning More
- •Selecting Chart Elements
- •User Interface Choices for Modifying Chart Elements
- •Modifying the Chart Area
- •Modifying the Plot Area
- •Working with Chart Titles
- •Working with a Legend
- •Working with Gridlines
- •Modifying the Axes
- •Working with Data Series
- •Creating Chart Templates
- •Learning Some Chart-Making Tricks
- •About Conditional Formatting
- •Specifying Conditional Formatting
- •Conditional Formats That Use Graphics
- •Creating Formula-Based Rules
- •Working with Conditional Formats
- •Sparkline Types
- •Creating Sparklines
- •Customizing Sparklines
- •Specifying a Date Axis
- •Auto-Updating Sparklines
- •Displaying a Sparkline for a Dynamic Range
- •Using Shapes
- •Using SmartArt
- •Using WordArt
- •Working with Other Graphic Types
- •Using the Equation Editor
- •Customizing the Ribbon
- •About Number Formatting
- •Creating a Custom Number Format
- •Custom Number Format Examples
- •About Data Validation
- •Specifying Validation Criteria
- •Types of Validation Criteria You Can Apply
- •Creating a Drop-Down List
- •Using Formulas for Data Validation Rules
- •Understanding Cell References
- •Data Validation Formula Examples
- •Introducing Worksheet Outlines
- •Creating an Outline
- •Working with Outlines
- •Linking Workbooks
- •Creating External Reference Formulas
- •Working with External Reference Formulas
- •Consolidating Worksheets
- •Understanding the Different Web Formats
- •Opening an HTML File
- •Working with Hyperlinks
- •Using Web Queries
- •Other Internet-Related Features
- •Copying and Pasting
- •Copying from Excel to Word
- •Embedding Objects in a Worksheet
- •Using Excel on a Network
- •Understanding File Reservations
- •Sharing Workbooks
- •Tracking Workbook Changes
- •Types of Protection
- •Protecting a Worksheet
- •Protecting a Workbook
- •VB Project Protection
- •Related Topics
- •Using Excel Auditing Tools
- •Searching and Replacing
- •Spell Checking Your Worksheets
- •Using AutoCorrect
- •Understanding External Database Files
- •Importing Access Tables
- •Retrieving Data with Query: An Example
- •Working with Data Returned by Query
- •Using Query without the Wizard
- •Learning More about Query
- •About Pivot Tables
- •Creating a Pivot Table
- •More Pivot Table Examples
- •Learning More
- •Working with Non-Numeric Data
- •Grouping Pivot Table Items
- •Creating a Frequency Distribution
- •Filtering Pivot Tables with Slicers
- •Referencing Cells within a Pivot Table
- •Creating Pivot Charts
- •Another Pivot Table Example
- •Producing a Report with a Pivot Table
- •A What-If Example
- •Types of What-If Analyses
- •Manual What-If Analysis
- •Creating Data Tables
- •Using Scenario Manager
- •What-If Analysis, in Reverse
- •Single-Cell Goal Seeking
- •Introducing Solver
- •Solver Examples
- •Installing the Analysis ToolPak Add-in
- •Using the Analysis Tools
- •Introducing the Analysis ToolPak Tools
- •Introducing VBA Macros
- •Displaying the Developer Tab
- •About Macro Security
- •Saving Workbooks That Contain Macros
- •Two Types of VBA Macros
- •Creating VBA Macros
- •Learning More
- •Overview of VBA Functions
- •An Introductory Example
- •About Function Procedures
- •Executing Function Procedures
- •Function Procedure Arguments
- •Debugging Custom Functions
- •Inserting Custom Functions
- •Learning More
- •Why Create UserForms?
- •UserForm Alternatives
- •Creating UserForms: An Overview
- •A UserForm Example
- •Another UserForm Example
- •More on Creating UserForms
- •Learning More
- •Why Use Controls on a Worksheet?
- •Using Controls
- •Reviewing the Available ActiveX Controls
- •Understanding Events
- •Entering Event-Handler VBA Code
- •Using Workbook-Level Events
- •Working with Worksheet Events
- •Using Non-Object Events
- •Working with Ranges
- •Working with Workbooks
- •Working with Charts
- •VBA Speed Tips
- •What Is an Add-In?
- •Working with Add-Ins
- •Why Create Add-Ins?
- •Creating Add-Ins
- •An Add-In Example
- •System Requirements
- •Using the CD
- •What’s on the CD
- •Troubleshooting
- •The Excel Help System
- •Microsoft Technical Support
- •Internet Newsgroups
- •Internet Web sites
- •End-User License Agreement
Chapter 39: Introducing Visual Basic for Applications
As macros go, this example is okay, but it’s certainly not perfect. It’s not very flexible, and it doesn’t include any error handling. For example, if the workbook structure is protected, trying to add a new sheet will cause an error.
Learning More
This chapter barely scratches the surface of what you can do with VBA. If this is your first exposure to VBA, you’re probably a bit overwhelmed by objects, properties, and methods. I don’t blame you. If you try to access a property that an object doesn’t have, you get a run-time error, and your VBA code grinds to a screeching halt until you correct the problem. Fortunately, several good ways are available to learn about objects, properties, and methods.
•Read the rest of the book. Subsequent chapters in this section contain additional information and many more examples.
•Record your actions. The best way to become familiar with VBA is to turn on the macro recorder and record actions that you make in Excel. You can then examine the code to gain some insights regarding the objects, properties, and methods.
•Use the Help system. The main source of detailed information about Excel’s objects, methods, and procedures is the VBA Help system. Help is very thorough and easy to access. When you’re in a VBA module, just move the cursor to a property or method and press F1. You get help that describes the word that is under the cursor.
•Get another book. Several books are devoted exclusively to using VBA with Excel. My book, Excel 2010 Power Programming with VBA (Wiley), is one.
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CHAPTER
Creating Custom
Worksheet Functions
As mentioned in the preceding chapter, you can create two types of VBA procedures: Sub procedures and Function procedures. This chapter focuses on Function procedures.
Overview of VBA Functions
Function procedures that you write in VBA are quite versatile. You can use these functions in two situations:
•You can call the function from a different VBA procedure.
•You can use the function in formulas that you create in a worksheet.
This chapter focuses on creating functions for use in your formulas.
Excel includes hundreds of predefined worksheet functions. With so many from which to choose, you may be curious as to why anyone would need to develop additional functions. The main reason is that creating a custom function can greatly simplify your formulas by making them shorter, and shorter formulas are more readable and easier to work with. For example, you can often replace a complex formula with a single function. Another reason is that you can write functions to perform operations that would otherwise be impossible.
Note
This chapter assumes that you’re familiar with entering and editing VBA code in the Visual Basic Editor (VB Editor). See Chapter 39 for an overview of the VB Editor. n
IN THIS CHAPTER
Overview of VBA functions About function procedures Function procedure arguments Debugging custom functions Pasting custom functions
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Part VI: Programming Excel with VBA
An Introductory Example
Creating custom functions is relatively easy after you understand VBA. Without further ado, here’s an example of a VBA function procedure. This function is stored in a VBA module, which is accessible from the VB Editor.
A custom function
This example function, named NumSign, uses one argument. The function returns a text string of Positive if its argument is greater than 0 (zero), Negative if the argument is less than 0, and Zero if the argument is equal to 0. The function is shown in Figure 40.1.
FIGURE 40.1
A simple custom worksheet function.
You can, of course, accomplish the same effect with the following worksheet formula, which uses a nested IF function:
=IF(A1=0,”Zero”,IF(A1>0,”Positive”,”Negative”))
Many would agree that the custom function solution is easier to understand and to edit than the worksheet formula.
Using the function in a worksheet
When you enter a formula that uses the NumSign function, Excel executes the function to get the result. This custom function works just like any built-in worksheet function. You can insert it in a formula by choosing Formulas Function Library Function Wizard, which displays the Insert Function dialog box. (Custom functions are listed in the User Defined category.) When you select
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Chapter 40: Creating Custom Worksheet Functions
the function from the list, you can then use the Function Arguments dialog box to specify the arguments for the function, as shown in Figure 40.2. You also can nest custom functions and combine them with other elements in your formulas.
FIGURE 40.2
Creating a worksheet formula that uses a custom function.
Analyzing the custom function
This section describes the NumSign function. Here again is the code:
Function NumSign(num)
Select Case num
Case Is < 0
NumSign = “Negative”
Case 0
NumSign = “Zero”
Case Is > 0
NumSign = “Positive”
End Select
End Function
Notice that the procedure starts with the keyword Function, followed by the name of the function (NumSign). This custom function uses one argument (num), and the argument’s name is enclosed in parentheses. The num argument represents the cell or variable that is to be processed. When the function is used in a worksheet, the argument can be a cell reference (such as A1) or a literal value (such as –123). When the function is used in another procedure, the argument can be a numeric variable, a literal number, or a value that is obtained from a cell.
The NumSign function uses the Select Case construct (described in Chapter 39) to take a different action, depending on the value of num. If num is less than 0, NumSign is assigned the text Negative. If num is equal to 0, NumSign is Zero. If num is greater than 0, NumSign is Positive. The value returned by a function is always assigned to the function’s name.
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