Creating a Permission to Direct Ship only.

We have a billing clerk who is having difficulty invoicing direct ship orders. If the order is mixed with direct ship and ship re-ship and/or stock shipments, she inadvertantly always ships the incorrect product. For the direct ship items, the billing clerk needs to “ship and invoice” in order for the account payable clerk to pay the vendor. This is a nice feature in Navision to avoid direct ships not being billed. What I would like to do is set a permission that will allow the billing clerk to only “ship and invoice” those items that are direct ship on a sales order. Ship re-ship and out of stock orders will not be affected even if the billing clerk tries to ship the items by accident. The warehouse manager is responsible for shipping everything with the exception of the direct ships. The billing clerk is only responsible for shipping the direct ships. My question is, can I set a permission for the billing clerk whereas only the direct ships can be shipped? If so, could you offer a little insight in that area? If not, what is an alternative way to only allow the billing clerk to be able to ship direct ships? Thanks…