Column data based on start date

Column data based on start date

I have data that is start date specific for several types of products.  For instance, I have a customer that will begin buying chairs in Dec. another buying chairs starting in January but also buying desks starting in November.  I want to create columns for the next 3 years, that look at the start date, calculate the revenue from the sales of the item, and add it to that column.  Each sales activity is a separate row and I would just like to carry that information out to additional columns in the form. 

Widget, Price, QTY, Start Date:  Sept 1, 2010  Oct 1, 2010, Nov 1 2010 etc.  If the widget sells in Oct.  I want Sep to say 0, Oct to reflect the revenue, Nov. to reflect the revenue and so on.

This will give me a simple way to provide operations with a forecast by month.  I am new to this program and script writing.