I haven't tried it myself, but you can give it a shot:
Use CurrentProject.CloseConnection() to and set CurrentProject.Connection to
"Nothing" when a user "log off" your ADP app without quit from it. When next
"log on", use Current.OpenConnection() to reconnect APD app to SQL
Server/MSDE. Of course you provide a "log on/off" form in the ADP app, don't
you?