invoice verification system permits even after payment..is done..

Dear Sap Guru's ,

My issue is if P.O value is 10,000/- inr..

users are creating invoice park for 1000/- then invoice verification for 1000/-

( like frame work P.O )

After this process continoues for 10 times i.e.

invoice park & invoice verification for 1000/- , Ten times ..system still allows user to proceed for 11th time invoice parking and invoice verification..

can we put a complete check automatically..by any of the settings either in Invoice or SPRO...

Thanks in Advance....