MS Shared Fax problem

A client is faxing from navision using the Microsoft Shared Fax Driver on EXCHANGE\SharedFax running Exchange 2000 and Small Business Server 2000. In the Fax Wizard, they can not change any of the text fields (such as fax# & subject). They can when faxing from Word. Navision Support says to use an Automation variable, but they can not give more details. I created an Automation variable, but I don’t know what to put in the Subtype field and what to do from there. Any ideas?