Contract Agreement having complex pay items and delivery of items

Greetings everyone !!

We have license for iProcurement, Service Procurement, iSourcing, Procurement Contracts, iSupplier and Purchasing for Procurement.

Client uses single Contract agreement for Procurement of Services, Maintenance, office supplies(Consumables), Spare parts. Now for this client ask Contractors to give a composite price for everything. And ask for his payment based on Pay items agreed.

Now for office supplies, a list prepared with all stock items covered in the contract with quantities required to be delivered during the contract period. Now whenever the need arises logistic requests the Contractor for supply of goods. Now since we have already agreed the quantities contractor is required to provide we do not follow RFQ-Quotation-Purchase Order process, Instead we create releases for the Agreements.