[PrinceKumar]

Create two new variable you can named it as u want for example :
new mVehicle[MAX_PLAYERS];
new nVehicle[MAX_PLAYERS];
// now go under any callback where u wanna to call ur function here i will like to call my function under onplayerenterindyanmicarea(or whatever it is) callback
//here u also need some conditions , here think i have an specified area name mzone
// here only for example
if(getPlayerDynamicArea(playerid,mZone))
{
if(pressedkey == LEFT)
{
nVehicle[playerid] = CreateVehicle(...);
DestroyVehicle(mVehicle[playerid]);
}
}
note : it is a example which i m giving n functions are differ from actual functions