Double Invoice

All,

Suppose I have a PO for 100 KG. Then I have done GR for this PO for full quantity .

Now done Invoice verification for 100 kg .

Now if again I am doing Invoice verification for some quantity against the same PO ,its allowing me to do it .

I have already activated 'Set check for double invoices ' in SPRO .

Now how I can prevent this double invoicing .?

Kindly advise.

regards