How are others using Retainage in AP.

We are looking for a solution to record retainage to a separate GL account and then releive that entry when it is paid.  The invoices do not come in on a set schedule and can vary in amount, however do have a set % to be retained.

From what I see it looks like you can create the retainage through the recurring contract setup and define an amount or % to be retained.  Then these have to be released by a schedule to AP and or PO.    The vouchers create with a line for retainage that is on payment hold, but it cannot be charged to a separate account.