[jlalt]

You can use OnVehicleSpawn callback for that purpose ->
https://sampwiki.blast.hk/wiki/OnVehicleSpawn

and also you can use GetVehicleDistanceFromPoint to check if vehicle is in range of point or no.
https://sampwiki.blast.hk/wiki/GetVehicleDistanceFromPoint [ an ex ]

@ rip oma : p