Sending PO Outbound with change or create

Hello Gurus,

I need to generate and send the IDOC when creating or changing the PO. My question is do I need to configure two Message Types ORDERS and PORDCH in the same Partner Profile and Distribution Model?

Also how do I tell the output determination that it should trigger the Message Type for creation (ORDERS) or change (PORDCH)?

Experts please I need help.

Thanks in advance,

Primo.