Blocking Quantity in Sales order

Hi,

We have a requirement to block Quantity in sales order.

PP is not integrated with Sales order, its a MTO ( but actually client does not follow MTO in SAP)

Once the production is completed for that sales order......he want to block the sales order quantity either manually or automatically ( they use a z transaction to declare production complete against sales order ) but this should not stop him doing delivery and billling.

Please let me know how can we do this.

Thanks

Venkata Rama Reddy.K