Zeeshan,

I think you are making this too complicated. You appear to only want
the overall, in which case:

If you add a column D, then multiply B and C for each row (eg.
"=C5*B5"). Then total column D.

Alternatively add a total to each column, B & C and the multiply them
together

You are getting the "Too Long" error as you are putting too many
entries into one calculation.

Steve