Services has a only celling value but the quantity are not defined

Hi Gurus,

I have testing the cycle of Complex PO using Purchasing to workconfimation and Payment to the Supplier based on the Progress of the Work Confirmation.

Here are few Queries i would like to understand and how this can be mapped in the system to achieve using Complex PO/ Service Procurement.

Most of the Services the business carries is non committed quantity which vary based on the service provided/required.

These Services has a only celling value but the quantity are not defined.

As on date business using Contract pruchase Agreement and based on the service used they create PO and make the payment for the services which is used.