Discount Condition

Dears,

I have this scenario where i m create PO with different line items where some of these item has account assignment (Non valuated material), supplier offer me discount in term of amount ex USD 2000, but this discount needs to deducted from the item with account assignment.

other items in the PO which is the stock item (Non acc Assign) doesn't needs to be affected with such discount

hope the scenario is clear.