How do I Find the Username of a Mailbox other than my own in LotusScript

Hello,
  I have written a Public shared Agent that exports selected E-Mails for a given user to a file for Optical storage.  One of the fields used to identify the document in storage is the User's Name.  I currently get the Username from the property "CommonUserName" from the Current Session.  This works fine while users are archiving there own E-Mails, but it creates a problem when users Archive E-Mails on some else’s behalf.  When I run my script on another users Mailbox from my notes session the E-Mails are identified as being mine instead of the proper user.  This is a problem for the secretaries at my location for the do the Archiving for the Bosses.
  So ultimately what I'm asking is how do you determine in LotusScript the Username on a specific Mailbox, not on a Specific Session?