Say A1 is either AB or AC
and B1 is the calculation eg =SUM(B5:B10)

change B1 to =if(A1="AB",SUM(B5:B10),"NULL")

Danny

"sedonovan" wrote:

hi everyone,
i wonder if you could help? i need to develop an IF formula so that if one
cell AB it performs the calculation, if it = AC it returns null (NOT ZERO
though!). the two values will only ever be AB or AC.
help. please!
thanks!
:o)