Sounds like a pivot table is ideal for this...

http://peltiertech.com/Excel/Pivots/pivottables.htm

In article ,
DKY wrote:

I have a txt file that I pulled from our system here at work and it is a
list of part numbers in one column (column D), demand for each location
month 1 (column E), demand for each location month 2 (column F), demand
for each location month 3 (column G) and cluster codes (column C). The
cluster codes are groups of locations. I want to write up a
conditional statement that will look at the part numbers and the
cluster codes and add up a total demand for month 3 a total demand for
month 2 and a total demand for month 1. Is there a way that I could do
that?