Can't assign value to an object

[BobMcL]

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' please have a look at it, thanks.
Gamez System

 

[gromit]

Hi -

The message you are getting is because of the referential integrity between the InvoiceDetails and Products tables. Each record in Invoice Details must have a valid product ID, but you may not have created it yet.

You need to establish a valid product ID first and then select it (perhaps via a combo box).

- g