AP prepay event oracle.apps.ap.invoice.prepay

Hi,

I'm trying to use this event

oracle.apps.ap.invoice.prepay

I have created a subscription, which for now just inserts a row into my test table. But I can't see the event being raised at all. I've looked through all source and can't find any code that raises this event, unlike say oracle.apps.ap.invoice.hold.

Does anyone know if this event is actually implemented? If so, is there any setup that needs to be done to enable it to fire. If not what steps need to be taken to get it to fire. Simply applying/unapplying prepays doesn't appear to do it.