Ahh, that keyword "vehicle". It's pretty useful to search. And the func_ that should be used is "func_vehicle".
Anyways, I still can't understand how to calculate the time that player has used the vehicle. Like I am searching for function which will be called all the time while the player holds the button and drives. And is this ham such a function? Or it's called on the first pressing of the button. I need that info, too, and then I could fix my problem.