Release 11i. Return to vendor for invoice already matched to a receipt. Not using debit memo creatio

Hello,

if an invoice is matched with a PO/receipt, no quantity hold generated assuming qty billed same as qty invoiced, then for this PO line a return to vendor is done.

The invoice will not go on hold if quantity received less than quantity invoiced.

How to allow AP to have invoice on hold(also if already paid but so AP can track this and ask for credit memo) when a return to vendor done later will decrease quantity received?

Thanks

Antonio