Delivery Address country field in purchase order

I have a requirement to write a validation on Delivery Address Country field, whenever user changes this field (By default PLANT address is there) i need to read this one to perform some validation while CHECK or SAVING the purchase order.

I am using the EXIT_SAPMM06E_012 but during runtime i don't see any data in the structure MEPOITEM related to delivery address. Some body provide me the way to read DELEIVERY address country.country.jpg