if(IsPlayerInRangeOfPoint(playerid, 2.0, X, Y, Z))
{
//what happens if you are in range
}
else
{
// what happens if you don't are in range
}

#define PRESSED(%0) \
    (((newkeys & (%0)) == (%0)) && ((oldkeys & (%0)) != (%0)))

public OnPlayerKeyStateChange(playerid, newkeys, oldkeys)
{
    if (PRESSED(KEY_CROUCH))
    {
        if(IsPlayerInRangeOfPoint(playerid, 2.0, X, Y, Z))
                {
                     //do something, like gates?
                }
        return 1;
    }
    return 1;
}