receive the material agsinst the same Purchase order

Dear Experts,

There is a situation here :
My client will use the Purchase return orders of NAV for return of spoiled items for which replacements will be sent by the vendor.
Now, these replaced items are entered into the system with a new GRN but the old PO and invoice has to be called as the vendor does not send new invoice for this.....

that means i need to receive the material with same purchase order.

Can any one suggest how this can be met in NAV???

any help really appreciated.