Regarding purchase order

Hello,

Im modifying purchase orders using the bapi BAPI_PO_CHANGE. But the problem is that after this bapi is used, it doesnt return any sy-subrc in order to know that the task was completed succesfully.

So the question is how i can know when a purchase order is being treated or modified by another user since the bapi doesnt return any value different than 0 in the sy-subrc.

Regards,

Roberto.