Is the goal to display your VB6 form when a particular Outlook folder is selected? In pseudocode that would be

Private Sub objExpl_FolderSwitch(

'your condition for displaying form here, based on particular folder name, default item type or whateve
If objExpl.CurrentFolder.Name = "Calendar" The
    With frmYour
         'set properties her
         .Show vbModa
         'retrieve properties her
   End Wit
  'clean up form object now or reuse and clean up when the add-in unload
  Unload frmYour
End I

End Sub