hi guys need help with nested data
thanks before and sorry if my english bad

i have 4 form
form 1 = Date In
form 2 = From
form 3 = Item List
form 4 = Serial Number

this is my relationship pic

this is what i want to make


the problem is:
1. when fill same supplier but different date = can't
2. when fill same item but different date & supplier = can't too

what i want is for example on date 5/8/12 supplier alex sent keyboard and mouse, and 6/8/12 alex sent again keyboard and mouse
how to solve that
thank you



Copy of Buy.zip