Thanks Hannah,
Your answers led me to a solution. I was confused by a false memory that the EDITFORM appeared automatically when selecting an editable feature, but I believe that is only for newly added features. What I needed to do was show the customized editform when an editable feature is selected. You can't use the Show method so your answer "...you can use the Feature Properties Tool" led me to use the featureproperties command, Application.ExecuteCommand("featureproperties"), when a feature is selected.
Keith