Progress Payment and Liquidation

We are on Release 11.5.10 and we have procurement contracts, iSupplier, Sourcing, and financial suite. Our client is looking for best way to handle contract financing payments such as progress payments / performance based payments or simply advances to suppliers.

This advance payments shd be tied to a PO and should be able to liquidate the same when actual delivery invoice payments are made.

Has anyone implemented something like this in commercial or public sector clients?

Any pointer will be greatly appreciated.