i have PO with Quantity 10 and received it then i billed it , after that the user's want to return the PO , and cancel it .
they did it .but what i want to disable the cancel from the PO if there is a billed quantity .
be careful about what you are about to do
1. If the bill is paid then cancelling a paid PO will become a audit issue. Not sure if oracle will even allow this but since you are thinking personalization it will be a good test
2. If the a return is processed then why not issue do the adjustment using credit or debit memo whichever is applicable.
3. what about inventory -- the product is either returned or received (partial in your case) and now you are cancelling the PO lines that is tied to this inventory txn. this may again become an audit issue.
Perhaps I am over thinking it but wanted to make sure the implications are discussed.