I've seen a lot of threads addressing changing formulas to values, but
haven't come across one going the other way. I have a spreadsheet that gets
created with all values. Column E is the sum of columns C and D. I'm trying
to figure out the code that will go through column E, and at every occurance
of a number, replace that number with the formula =C+D.

I tried using Isnumeric as a test, but it plugged that formula into all the
blank cells as well.
If IsNumeric(ActiveCell.Value) Then ActiveCell.FormulaR1C1 = "=RC[-2]+RC[-1]"

Suggestions?