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Please Note: This article is written for users of the following Microsoft Excel versions: 97, 2000, 2002, and 2003. If you are using a later version (Excel 2007 or later), this tip may not work for you. For a version of this tip written specifically for later versions of Excel, click here: Understanding Functions in Macros.
You already know that you can use subroutines in your macros. VBA also allows you to define functions that can be used in your macros. The difference between functions and subroutines is that functions can return values, whereas subroutines cannot. Consider the following macro:
Sub Macro1() TooMany = TestFunc If TooMany Then MsgBox "Too many columns selected" End Sub
Function TestFunc() TestFunc = False If Selection.Columns.Count > 10 Then TestFunc = True End If End Function
The macro (Macro1) calls the TestFunc function. This function returns either the value False or True, depending on a test it performs. Macro1 then acts upon the value returned. Notice that the function name can appear on the right side of an equal sign. This makes functions very powerful and an important part of any program. Within the function the result is assigned to TestFunc, which is the name of the function itself; this is the value returned by the function.
As with subroutines, you can also pass parameters to your functions. This is illustrated in the following macro:
Sub Macro1() A = 12.3456 MsgBox A & vbCrLf & RoundIt(A) End Sub
Function RoundIt(X) As Integer RoundIt = Int(X + 0.5) End Function
This simple macro (Macro1) defines a number, and then uses a message box to display it and the result of passing the number to the RoundIt function. The output is 12.3456 and 12. Notice that the parameter should be passed to the function within parentheses. Also notice that the function does not use the same variable name as it was passed. This is because VBA reassigns the value of X (what the function needs) so it matches the value of A (what the program is passing to the function). The important thing to remember in passing parameters to functions is that your program must pass the same number of parameters as the function expects, and the parameters must be of matching types and in the proper order.
ExcelTips is your source for cost-effective Microsoft Excel training. This tip (2259) applies to Microsoft Excel 97, 2000, 2002, and 2003. You can find a version of this tip for the ribbon interface of Excel (Excel 2007 and later) here: Understanding Functions in Macros.
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