Can't assign value to object (1 Viewer)

I keep getting this message when I try and input a product ID in the subform in my 'Order Form', the message says 'you can't assign a value to this object' and when i try to click the row below it says 'You cannot add or change a record because a related record is required in table 'Invoices'', how can I change this? do i have to relate it to the Products table and if so how do i do this? Thanks, Bob.

System Link:
Gamez System

I could be totally wrong, but it sounds like your subform is linked to your main form and in order to start entering data into the subform you need to have a record to associate it to. Try entering data into the main form first and see if that helps any. Best of luck.

alteque