Need your help badly re: sales and inventory system

Submitted by jaydc84 on
Sir, I am having a problem with regards to my project which is a sales and inventory system. here is the scenario: tbl inventory stockid itemid stockonhand expiration_date st-0001 it-0001 100 09/20/2012 st-0002 it-0001 50 09/30/2012 the customer orders 125 of it-0001. i would like to first deduct 100 from st-0001 then the remaining 25 i would be deducted from st-0002. i am really having a hard time with this. tnx and more power