See if this works for you:
Instead of Find/Replace....
Select the range containing the blank cells you want impacted
<edit><goto>
Click the [special cells] button
Check: Blanks
Click the [OK] button
That will select the blank cells in that range.
Press the [F2] key to begin editing the active cell.
Enter the formula, being mindful of the workings of relative references
Then...Hold down the [ctrl] key and press [enter]
That will put the formula in each blank
Is that something you can work with?
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Regards,
Ron
XL2002, WinXP