can i execute a command before recording or for that matter using the tv tuner (from mythtv)?

because i sometimes stream a tv channel using vlc and when i show is supposed to record while a tv channel is streaming mythbackend/frontend freeze

i want to kill vlc before utilizing the tv tuner

Yes, by abusing the external tuner script mechanism. Search for post by me tha mention delayed_settings for more details of how it works and how to use it for other purposes.