SAP Newby - What PO type/process to follow - Ongoing Contractor Services

Hi

I am working with a company that engages ten 3rd party service providers to perform tens of thousands of pieces of work each year. Each piece of work relates to a program and a location (tens of programs and thousands of different locations). The company wants to report costs down to location level and report both committed and spent (ie GRNed) amounts. Each piece of work is unique and it's cost varies. The details of the work to be performed under each program is not known at the begining of the year, however a total estimate of costs is available per service provider.

Rather than use a seperate Purchase Order per piece of work, what other type of Purchase Order is suitable?. They have previously used a Service Purchase order per service provider for a quarter, however this has been problematic. They want to minimize administration work. Any recommendations?