Using Data Validation on cells with formulas

[andrewb90]

I am using Data validation on a group of cells to make a popup appear if cell M3 is not valued between 1-5. Now Data validation will not occur since M3 gets filled in automatically from another worksheet.
Can I make some sort of macro button that will go around this problem?

My original idea is to have the macro when clicked:
Unprotect the worksheet
unhide row 3
click on cell M3 (and if necessary retype the formula in it)
rehide row 3
and hide an image on the page using the image name
then reprotect the worksheet

Would this work to satisfy the the data validation issue that seems to occur for me?

Any thoughts or suggestions on this issue would be greatly appreciated.

- Andrew