Importing Sales Orders existing customer with Primary Ship To assigned

When importing a new Sales Order the Primary Ship To Code is assigned to the new order even though a different address is imported and Ship To code is not even used in the import.  I don't want the Primary Ship To code to be assigned to an order that is imported.  I do not have anything assigned to the Ship To code on import.  To stop that from happening do you think I could add it to the import and assign null or something to that field to stop it from being populated?