You can create Purchase Orders using the Vendor Availability.
Creating PO from the vendor availability
As soon as you start creating Prebooks from Vendor Availability the system will automatically place those items into an existing purchase order or a new one, based on these rules:
The system will add the product line to an existing PO as long as it matches the vendor name, ship date and its status is "PA" (Pending Approval).
The system will create a new PO if there are no matches for the criteria described above, in addition, the PO will be created with a "PA" status.
Deleting items from Prebooks and POs
The system allows you to delete a line item from a prebook that has been added to a purchase order as long as the PO is not approved or confirmed by farm, in other words, the PO status cannot be "A" or "CF".
If the line item is removed from the prebook and the PO status is "PA" (Pending Approval), the line item will be removed from the PO as well.