if (constant == 1)
{
    if (max_time == -1)
        totaltimer = -10;
    timer++;
    if (timer >= rate)
    {
        if (i_ex(target) && totaltimer < max_time)
        {
            event_user(0);
            timer = 0;
        }
        else
        {
            instance_destroy();
        }
    }
    totaltimer++;
}