How to create PO matched prepayment with retainage.

We have requirement :-

PO created with 10000 amount.

Prepayment 1 created with 1000 amount.

Prepayment 2 created with 1000 amount and 10% retainage.

Invoice 1 created with 3000 and 10% retainage.

Invoice 2 created with 3000 and 10% retainage.

Invoice 3 created with 4000 amount and 10% retainage.

We can handle the invoice scenario by creating multiple PO line with different line amount and retainage %.

However we can not apply retainage to prepayment. Please suggest if any other option to achieve this …