Exit in MIGO

Hello,

I want to know if there any exits (user/field) in MIGO transaction for the following purpose:

I want to do some checks on the PO number/Item intered when you do goods issue to purchanse order. For this I want to findout if I can use any user exit or if I can create a field exit on screen 2000(GODYNPRO-PO_NUMBER & GODYNPRO-PO_ITEM)

Thanks

Ramesh