If you create a new profile, then create a command containing only the "Start Dictation Mode" action, I.E.
Start Dictation Mode
save the profile, execute the command, hold down button 18 on your joystick, and speak any phrase that isn't that of the command you just created (E.G. "this is a dictation phrase"), is there an "Append Dictation Buffer:" message in the log on VoiceAttack's main window?