Inter-Department Internal Order Process - R12 iProcurement, Inventory and Order Management

We have the following process for internal orders (iProcurement, Inventory and Order Management) and I would appreciate anyone that may have a practical solution. 

Internal requisitions are raised for stocked items, a sales order generated which is picked and ship confirmed.  Currently at ship confirm a customised journal is created and therefore a customer invoice is never generated or required. The customer invoice is not required because no physical payment is made by the internal buyer/customer only an accounting movement (from one cost centre to another) is required - (single operating unit with a single store that issues stocked items to departments within the organisation).