Create a trigger. Group it to the player. (Yes, as if you wanted to put the trigger in the player's group.) Now you will have new options in the Activation box
Activation: group leader present (or whatever you want)
Type: Switch
Effects: whatever track you want
Now create the waypoints for the guard. They will be something like
move
move
cycle <--------- snychro the trigger with this waypoint
seek & destroy
cycle (you must put cycle next to S&D otherwise he will stop eventually)
Leave the condition field as it is. (this)