[Oi!]

I'm trying to make it so that the player has to be within a sertain distance of their car to /lock it, so say the players car is on the other side of the map, it will say "You must be next to your car to use this command", the car is in the players file, so say you're next to the car, then you can use it, but then you get in the car and drive it to EG: the bank, get out and type /lock, try to type /unlock inside of the bank and it says "You must be next to your car to use this command", can anyone help me?