setting for recording from sound card only when playing

Audacity 2.1.1 window 7 pro

any setting for recording from sound card only when sound is being played? i want to record several tracks while away from computer. thanks

i was given this solution which i thought was the answer (Edit → Preferences → Recording → Sound Activated Recording) but when i tried it, it didnt work. still keeps recording nothing.

Sound Activated Recording will record whenever the input signal is greater than the “activation level”. If the background noise is greater than the activation level, then the recording will be continuous, in which case you need to raise the activation level so that recording is not activated by the background noise. See: http://manual.audacityteam.org/man/transport_menu.html#sar