which user exit suitable for purchase order inbound idoc.

Hello experts,

which user exit suitable for purchase order inbound idoc.?

I am new to IDOCs and EXITS.

My requirement is

PI system sends IDOC to our SAP system.

IDOC type is PORDCR102

MESSAGE TYPE IS PORDCR1

before saving te purchase order our exit should trigger and modify some item data .

can u send sample code(reading segments) for that exit.

Regards,

Revanth.