Inbound Invoice cannot be posted if there is no GR for the PO

Hi,

we are having a process of Posting Invoice to the PO from Inbound Idoc coming from 3rd party system. Now we are having a issue, if the PO does not contain GR, the Invoice is created but not posted and not updated in Po History tab. The reason being is since GR is not present, the system is asking for some approval when we click that approved icon, automatically the quantity and amount are being populated in invoice and it is ready for posting.

Is there any way of automating above process of posting Invoice from Idoc when GR is absent for the PO? Anybody have come across this type of process?

Please share your views on how this can be handled.

Thanks

Navin