XL97: Calculation Problems with Arrays in Custom Functions

• Microsoft Excel 97 for Windows

SYMPTOMS

When you use a custom function in a workbook, the function may return incorrect values. Recalculating the workbook may also take longer than it does in earlier versions of Microsoft Excel.

CAUSE

This problem occurs when the following conditions are true:

• The custom function references a range of cells.

      -and-
  

• You enter the custom function across multiple cells as an array.

      -and-
  

• You recalculate the custom function.

WORKAROUND

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1. Add the Volatile method to your Visual Basic for Applications custom function. This line must immediately follow the Function statement. For example, the following function uses the Volatile function:

         Function MyFunction(InputRange) As Integer
            Application.Volatile
            MyFunction = InputRange * 10%
         End Function
   
   

2. Reenter the formula that contains the custom function. To locate and select the number of cells that comprises the array formula, follow these steps:

   a. In the worksheet, click any one cell that contains the custom

         array function.
   

   b. On the Edit menu, click Go To. In the Go To dialog box, click

         Special. In the Go To Special dialog box, click Current Array.
   

         Every cell that is in the array is selected.
   

   c. Press F2 to edit the entire array. Press CTRL+SHIFT+ENTER to

         reenter the array formula.
   

3. Save the workbook.

STATUS

Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article. This problem was corrected in Microsoft Excel for Windows, Service Release 1, and in Microsoft Excel 98 Macintosh Edition.

MORE INFORMATION

Arrays in Microsoft Excel 97 are recalculated <n> times, where <n> is the number of elements in the array. In earlier versions of Microsoft Excel, the array function is recalculated only once. Therefore, the number of elements in the array is directly proportional to the decrease in performance when the array is recalculated. Depending on the calculations Microsoft Excel performs in the custom function, incorrect values may be returned. For example, an incorrect value is returned if the function increments a counter and uses the counter value as part of a calculation.