Adding more than 1 invoice to a bill or purchase order

sometimes a supplier may send you 2 or more invoices for your purchase order.

Rather than having to alter the original purchase order to reflect this, then making a new purchase order from scratch, a facility to add another invoice or supporting document to a bill would be great. It doesnt need the prefill option etc, it just needs to be there.

also there shoule be a facitily for recurring purchase orders...