I have a problem with my sumproduct formula. The formula returns the correct
information if the range is filled in, but if the range is not filled in and
the cells in that range are empty, I get an error message. How do I get it to
return the correct amount even if all the cells in the range are not filled
in?

Here is my formula I am using:

=SUMPRODUCT((Zone=B8)*(O2scfm0)*(O2scfm*diversity ))

Zone is a range of cells from $C$5:$C161 it seems to happen in each of the
ranges I have. even if I change the ranges to actual $C$5......etc then it
stills gives error.

any ideas on how to return a correct number?