V8 Customize Customer Shipment Entry

For reasons I will not try to explain we make shipments against closed
sales Orders. In previous versions of Vantage we have had to work
around not being able to make a packing slip for a closed sales order.
Now that we can customize things in version 8 I would like to be able
to make it possible to enter a closed sales order number in customer
shipment entry. Could anyone point me in the right direction to do so?