Milestone Based PO

We have a situation wherein we procure certain high value inventory items. We pay for these items based on certain milestones. The amount to be paid at each milestone varies from each item and supplier and the negotiation we have with the supplier. We want to know if this can be implemented in the PO module using standard functionality. These items will be inventory items and we need to know how the receipt of these items would be done if we have milestone based payments.
Please advise.