Field Problems with MS Project 2000

Here is my problem:

I want to insert a number of custom cost fields in a task sheet, so that the
individual figures in these fields will be added to the ‘Total Costs’ Field. Or to word it differently, I want to have more than one ‘Fixed Cost’ Field operating in the one sheet. I’ve tried to no avail, so am wondering if this is actually possible.

Thanks in advance….