You can put VoiceAttack into "standby" or "sleep" mode either by clicking the headphone icon on the main window, or running a command containing the "Make VoiceAttack Stop Listening" action.
To get VoiceAttack out of sleep mode, either click the headphone icon again, or run a command with the "Make VoiceAttack Start Listening" action.
While listening is turned off, spoken commands will only execute if they have the "Make VoiceAttack Start Listening" action at the very top of the action list.