I have two worksheets I am working on. On one worksheet I have the same
project number listed multiple times with $ amounts listed by months. On the
other worksheet I need to sum the $ amounts by project number and by month.
How can I do this with reliable accuracy?

Data example:
Project # Month Amt $
4004 Jan-07 50
4004 Jan-07 25
5005 Feb-07 35
5005 Feb-07 40
5005 Jun-07 50
6006 Apr-07 75