Display Message Box if any cell value in range is modified

Hi

I want to alert users with a message box containing the following question: "Prior Valuation - Are you sure you want to edit this worksheet?" Ans(Y/N), should the user attempt to edit any cells within a specific range ("C2:AS100") on the worksheet, say Sheet3.

Ideally, it would only pop up the first time the user attempted to make a change to a value within the range. Therefore, if the user say 'Yes', it will not pop up again until the user returns to that worksheet again from another worksheet in the file and attempts to edit a cell value within the C2:AS100 range once more.

I have 300 files that I need this to be applied to, so I plan on implanting the macro from a central source workbook into each workbook using another macro, if that makes any sense.

Thanks!

Ed

Pl see the attached file.
When any cell in C2:AS100 is selected pop up will come. If ans is 'yes' it will not show once again. If ans is 'no' again pop will show when another cell is selected.
Worksheet_selection event is used.
If it is OK mark the thread SOLVED.
Thanks.

Thanks - this works well!

I now want to apply the code to a specific worksheet in the 300 identical workbooks. The worksheet name is identical in each of the 300 workbooks as well ( 'Jun. 30, 2012').

Is there a way to roll at the macro and save each workbook? I don't want to have to run the macro from a central file.

Thanks in advance!

Ed