PLEASE HELP

I have a 30 page excel worksheet that I need to get a sum for. I have
hidden the cells that don't need to be included in the total, but I need to
keep them in the work- sheet. How do I calculate these cells without having
to delete them. I thought about copy/pasting them into another worksheet to
see if they would come without the hidden cells, but thought their had to be
an easier solution?

Please help...Thanks in Advance