Hi Tricia

firstly unsure why you're adding a subtraction? AFAIK
=F11-E12
would serve you just as well, if not better.

what about other formulas in the workbook .. are they working okay? if not,
you might like to check that calculation is set to automatic, tools /
options / calculation tab

Cheers
JulieD

"Tricia" wrote in message
...
Hi:

I have a formula in Excel 2002 - using XP that used to work and now I have
to take my cursor and touch the formula in the formula bar at the top of
the
screen and then hit enter which causes the calculation to take place. The
formula is simple =sum( f11-e12). I have this formula is several
different
worksheets and it happens in all of them. Help!!
Tricia