Looking for a formula for comparing dates and decreasing values
 

I am looking for a solution to an ongoing increasing problem with my
inventory control spreadsheet. I currently have a 2 sided sheet. The left
side is receivables that are date coded and the right side is for production.
I am currently unable to deduct from the right side using a date code from
the left side.
ex: rec. exp run qty
exp
5-2-08 5000 11-5-08 5-12-08 5500
11-5-08
5-7-08 4000 11-5-08 5-13-08 1400
11-5-08
5-10-08 3500 12-3-08

At this point the left side can not calculate the amout for each date code
and deduct the qty used on the right side while letting me know that I have
2100 left for date code 11-5-08. Is there a way to do this?