[Ceez]

No don't have to use an oldkey
you can use something like this

pawn Код:

if(!IsPlayerInAnyVehicle(playerid))
    {
        if(newkeys == KEY_YES)
        {
              SendClientMessage(playerid, -1, " You are not inside a vehicle. ");
        }
      }

This function says: if a player isn't inside a vehicle and he taps KEY_YES (known as Y) it sends him message he isn't inside a vehicle.