Help with a check in i my orderdetails.

[Mattias]

Hi

I have a main and a subform called Order and Orderdetails.
Order has its orderno as a autonumberfield and Orderdetails has its
orderdeatailsno as autonumber as well.
For every orderdetail I emter Inventory no in a combobox.
As it is now it is possible to enter several orderdetail rows with same
Inventory no.

I need help to add a check that the inventory no is accepted more than once
in the same order.

Is it possible?

Thank you in advance,

Mattias