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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: Forcing a Macro to Run when a Worksheet is Recalculated.
When you write a macro, it is designed to be run whenever you choose to run it. What if you need to develop a macro that will run whenever something changes in your worksheet? What if you want the macro to run automatically? This is particularly necessary if you are creating a custom function that you want to use within the cells of the worksheet.
This is where the Volatile method comes in handy. All you need to do is include the following statement within your macro:
This informs Excel that the results of the macro are dependent on the values in the worksheet, and that it should be executed whenever the worksheet is recalculated. For instance, consider the following user-defined function:
Function CountCells(MyRange As Range) Dim iCount As Integer iCount = 0 For Each cell In MyRange If cell.HasFormula Then iCount = iCount + 1 End If Next cell CountCells = iCount End Function
This function, if used in a cell, counts the number of cells that contain formulas within a specified range. However, the function will only run the first time it is entered into a cell, or whenever the cell containing the formula is edited. If you want the function to recalculate every time the worksheet is recalculated, you would add the Volatile method near the beginning of the function:
Function CountCells(MyRange As Range) Dim iCount As Integer Application.Volatile iCount = 0 For Each cell In MyRange If cell.HasFormula Then iCount = iCount + 1 End If Next cell CountCells = iCount End Function
The inclusion of the Application.Volatile method means that every time the worksheet is recalculated, this function (macro) is again run.
ExcelTips is your source for cost-effective Microsoft Excel training. This tip (2013) 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: Forcing a Macro to Run when a Worksheet is Recalculated.
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