Hello,
You could add some Lotus script (see below) to a button and send it to your users before the change (action button before leaving for the day). This would change the users current location document to point o the new server (need to modify xxx entries).
You can also take it one step further and script a button that builds a new location document with the new settings. Not sure how this will rok in R4, it's been years since I touched it.
Sub Click(Source As Button)
Dim session As New NotesSession
Call session.SetEnvironmentVar( "MailServer",
"CN=xxx/OU=xxx/OU=xxx/O=xxx" )
End Sub
Rgds,
John