You may find it easier to programmatically call the Save method on your workbook to replicate the Autosave feature in Excel.
The problems that you are experiencing may be down to the fact that the Autosave feature is an Excel Add In module and as such needs to be treated in a slightly different manner. In order to get access to the Add In, you need to manual load/install the necessary Add In when you open the ActiveX reference to Excel.
In Excel 97, the tree is as follows:
Application >> AddIns (Object & Collection) >> AddIn (Object)
From here you can Add a new AddIn but must set its Installed property to True in order for it to be "fully installed". The (VBA) help file included with your release of Excel will provide further assistance in navi
gating through to the appropriate methods and properties and more specific information regarding the loading and proper installation of Add Ins.
Personally, however, experience has shown that it is far simpler to just manually save the workbook using the SaveAs/Save methods as and when required.
Jeremy