Justin, If the PO has been approved, you can revise the PO to accomodate the alternate item. If you have not received any of the original item number, you can change the item number to the alternate item number on the original PO line. If you have already received some of the originally ordered item, then you will need to add a PO line for the alternate item. Be sure to allow invoices and receipts against the revised version of the PO. Once you approve the revision, you will then be able to receive the alternate item.