sounds like the cell is locked with a custom validation.......
i do that a lot with mine, so users can't change
my perfectly-planned-formulas. :)

on the main toolbar, try data........... validation............
& see if anything is already entered there or if it's all blank.
susan


DRLski wrote:
I'm trying to just add a simple formula to a cell in Excel "=sum(A1,
I1)" but unfortunately it seems to keep coming back with an error:

"Cell contains a Formula. Cannot Modify. Must Select Cancel."

I tried searching for this error but I came up empty. Anyone have any
ideas on what I am doing wrong?

Thank you,
Dave