OK, here's another way:
1. Unprotect the document.
2. Delete the formula field in its entirety;
3. Press Cmd-F9 to create a pair of field braces, thus { }
4. Input the formula into the field, thus {=REDEMPTIONGROUP/OFFERGROUP*100 \# "0.00%"}
5. Re-apply the forms protection.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]