How to apply lump sum discount on R12 Purchase Order

Dear All,

We have below requirement on Purchase Orders.

Example ;

PO number 158  having  ten items of total amount  11,500.

Supplier  agreed for a discount of 500 on total amount.

But the supplier do not want us to reduce the price of item price as their ISO policy will not allow discount on individual items.

Now  how we  can create a PO mentioning the Lump sum discount

Total PO amount 11500

Discount                  500

Net PO Amount 11000

Thanks..

Have Good Day..!!!