Exactly this is the problem. Using different radio trigger to every chopper isn't an option, because there's not enough radio triggers available. On the other hand, the special area shutdown works (engines of choppers in green zone will shutdown in 10 seconds from entering to zone). When chopper enters zone, three triggers will activate:
Activation BLUFOR, Present
On act. list_to_kill=thislist
Activation BLUFOR, Present
Countdown 10 seconds
On act. {_x setFuel 0} foreach thislist;
Activation BLUFOR, Present
Countdown 5 seconds (sync with shutdown)
On act. _handle = execVM "Shutdown.sqf" (=hint row "Ready..." "Set..." "Go!")
One more question; how to get rid of super annoying "File xxxxxx not found" notification that appears when I play a custom sound in multiplayer? The sound is played but everyone gets still the error message when trigger playing the sound is activated. Sound is in MPMissions\Mission\sound, and I have it determined in description.ext file (class cfgSound) etc.