Order qty and confirmed qty mismatch

Dear friends,

My requirement is System should not allow to go further if the sale order qty and confirmed qty(after avaialbility check) mismatch is there.Pls suggest.

Now currently system will check the availability qty and will show the information of confirmed qty in the another screen.and if we say continue the process, we can go ahead and save the document.but the document will be in open state.

So pls suggest the way i can go ahead for this requirement.

Regards

Mahendar.