MB1B: Sub contractor can receive the material multiple time against same PO

Hi,

We did 541 movt againt this order by MB1B transaction and transaction was complete and 6000 pcs materials showing to suppliers end.

But when we did again 541 movt against same PO number then system has accepted again 541 movt for 6000 pcs .

My problem is it should not be allow same po .What is logic for restrict when using same po in multiple times.

Thanks & Best Regards.

Balakrishna