PO number being able to select after PO is close in AP invoice Form

 Hi,

My scenario is this. We have created a PO with quantity 10 items & say PO number is 123. We use 4 way matching & it is received to inventory. Then the invoice come & we match it to

PO. In invoice entry form we enter PO number 123 at header level & match it then validate the invoice. Now if we go to the PO its status is close & approved.

Now if the user tries to enter another invoice to match for PO number 123, he s able to select PO number 123 at the header level which i think system must prevent the user

if the PO is closed. Then the user is able to go and match & in match process a note comes saying quantity overbilling but still the user is able to match. But when the invoice is validated