adding amounts if criterias are met

[Mercer]

I have a sheet #2 where I would like to automaticlly update totals from
another sheet. The values are being input on sheet #1. Sheet #2 should total
the amounts from sheet#1 based on a category. So the formula must be smart
enough to search sheet#1 for the category (there may be multiple of the same
category) and then take those values and add or subtract then from the total
on sheet#2. Thus giving me the current value for all activity on sheet#1 for
that category.

 

[Jim Thomlinson]

There are a number of solutions thta spring to mind.

The simplest just uses sumif functions
=sumif(Sheet1!A1:A100, "=MyCategory", Sheet1!B1:B100)

If you require to match multiple criteria then SumProduct formulas will do
the trick...
http://www.xldynamic.com/source/xld.SUMPRODUCT.html

If you want an automated solution that puts all of your ctegories into a
table then a pivot table would be for the best.
http://peltiertech.com/Excel/Pivots/pivotstart.htm