How to make a regan button on a car?

I have a obby, which has a lot of people. I have a small fort with 2 cars. I want to put a regan button for it so there is a car for everyone. Sometimes the regan button is odd, What I mean by odd is this.

Example: 2 cars is there. Say about 30 people is in the server. The regan button is there and 2 people took the car. when you touch the regan button. Sometimes the person Who took the car and the person regans the car, the car the person was driving disappears. That is the odd thing I don't want to happen.

Any help?