R12.1.3 Contingent Worker Expense Reports - What is the recommended approach to paying the agency an

Based on R12.1.3 functionality using Services Procurement, we are able to create a Contractor Request (requisition) and PO that includes an Expense lump sum amount for a Job Agency's (supplier's) contingent worker/contractor.  In Internet Expense, we are also able to have the contingent worker enter their reimburseable expenses.  This expense report can be imported into Payables and if the contingent worker has the Job Agency setup on their HR assignment record (on the supplier tab), the expense report will be reimbursed to the Job Agency.

So now that we have a contingent worker expense report with the correct project charges on it which will be reimbursed to the Job Agency, how do we tie this expense report back to Agency PO to relieve the open po line amount for expenses?