Order without quantity

[Anirban Ganguly]

Hi,

I would like to create a value contract where quantity is unknown & then I need to create invoices from that order based on the bill amount received from my Vendor. In iDempiere purchase order quantity is mantatory & user can not create invoices if invoice quantity exceeds order quantity. So how do I manage to create invoices from a purchase order by ignoring the PO quantity? Other than PO/SO is their any alternate value order available in iDempiere?