Collective billing document

Dear SD gurus,

I understand that standard SAP checks that when we perform collective billing (creating a single invoice for multiple Delivery Orders). The checking criteria is that the Sold-To party and Payment Terms muts be similiar (and a few other criteria).

I need to know if it is possible to add checking for Ship-To party and PO Number field must be similar before merging of the multiple delivery order into a single invoice is allowed. If yes... where do I perform this setting?

Thank you.