j = gridd - 30;
while (j > gridu)
{
    i = gridl + 10;
    while (i < gridr)
    {
        if (collision_point(i, j, obj_blackbox_o, 0, 1))
        {
            with (collision_point(i, j, obj_blackbox_o, 0, 1))
                event_user(3);
        }
        i += 20;
    }
    j -= 20;
}