if and isnumber, isnumber - then perform calculation.

I want a cell to do this calculation: ((RC[-1]-RC[-2])*24)-0.5

I'm trying to enter it so that the calculation only takes place if there are values in RC[-1] and RC[-2]. If either of those cells are blank, I do not want it perform the calculation.

This is the closest I've gotten: =IF(AND(ISNUMBER(RC[-1])),(ISNUMBER(RC[-2])),(((RC[-1]-RC[-2])*24)-0.5))

Yet, this only returns the word "true" in the cell. It is in fact true, but I want "true" to mean that it then performs the equation. I've tried tacking on a false value as well, but that says there are too many arguments.

Please advise.

I can finally tack on my false value as well! Thank you very much :-)