Unique accounting reqt - Invoice validated but not to accounted until..

All,

We have the following unique reqt.

Step 1 : Create an invoice in OU1, go thru AME, approve and validate the invoice.

Step 2 : Create an exact equivalent invoice in OU2 and pay the invoice as per payment term (say Net 30). OU2 should be making payment on behalf of OU1.

Step 3 : Once the invoice in OU2 is paid, then the invoice in OU1 should be accounted. Basically, the Charge & liability for invoice in OU1 should be accounted only after the payment of invoice in OU2.

Any form of suggestions or ideas welcome !