No, that's not possible. If you have configuration data that an Outlook application needs, use a StorageItem in Outlook 2007 or a hidden message (CDO or Redemption, not Outlook object model) in earlier versions.
"GP" <GP@discussions.microsoft.com> wrote in message news:3D5A31DC-7191-4847-8CED-BF83F8B0F82B@microsoft.com...
> Following Sue Mosher's advice (separate posting) I used the SaveAsFile method
> to copy a text file DocumentItem to a Windows file system directory where it
> can be opened and configuration data read. This works perfectly. However I
> would like to make the DocumentItem, its Attachments collection (of 1
> attachment) or the folder that holds the DocumentItem, invisible to the user
> but still accessible to code running in the user's session. This is to stop
> the user tampering with the configuration data. Is it possible to do this?
>
> GP