Purchase order qty issue

Hi SAP SD GURUS,

this is STO process, Doucment type is UB, delivery type is NLCC, Item catagory is NLC.

When ever to create the delivery enter the qty more than the purchase order qty, system is allow to create the delivery, in this case i want restirct the delivery levle and we cannot enter the delivery qty more than the Purchaswe qty in delivery level, where it is controlled?

Thnaks and Regards,

Murali krishna