Multiple column summarization - Excel 97

My plant manager has a spreadsheet he uses to post planned production. My job is to total the number of pounds of each product (there are over 70) for futire dates. The three columns of relevant data are Product, pounds and start date. I created an additional column to convert the start date to an M-YY date field, since the month of planned production is the relevant time period for the summary, though the actual date is important for the production.

The fields containing the results need to be linked to the Purchasing Manager's spreadsheet so he can use the data to calculate how much raw materials to buy.

I don't know how to proceed. All suggestions appreciated!