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Chris uses a data validation technique that successfully stops non-unique information from being entered in a column. (This technique was described in previous issues of ExcelTips.) He rightfully notes that there is still a problem with data validation, however: Someone can paste information into a cell and successfully bypass all the checks in place.
For instance, if you type "George" into cell A8, and then type "George" into A9, regular data validation will generate an error, as one would expect, indicating that the value you are trying to enter is not unique. However, if you type "George" into cell A8, copy that cell and paste it into cell A9, no data validation error is triggered--the paste is allowed.
There is no direct way around this in Excel. You can, however, cause Excel to do some checking whenever you try to do a paste. Consider the following macro:
Private Sub Worksheet_SelectionChange(ByVal Target As Range) On Error Resume Next For Each TmpRng In Target TmpVal = TmpRng.Validation.Type If TmpVal > 0 Then If Application.CutCopyMode = 1 Then MsgBox "You cannot paste into validated cells." Application.CutCopyMode = False Exit Sub End If End If Next End Sub
This macro is only run when the selection changes in a worksheet. (This code needs to be in the code window for a worksheet.) It examines the target cells (the ones being selected), and if the user is trying to paste into a cell that has validation active, it will not allow it. Further, the user will see a dialog box that indicates the error.
You should note that this routine just checks to see if pasting into a data-validated cell is being done. If it is, then an error is generated. The routine does not check to see if what is being pasted is actually permissible under the validation rules in the target cells; that would be much more complex and require quite a bit more coding.
ExcelTips is your source for cost-effective Microsoft Excel training. This tip (2449) applies to Microsoft Excel 97, 2000, 2002, and 2003.
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