var mx, mxid;
mx = -1;
with (enemy)
{
    if (aggro > mx)
    {
        if (collision_circle(x, y, 400, player, 0, 1))
        {
            if (collision_line(x, y, player.x, player.y, nopass, 0, 1))
            {
                mx = aggro;
                mxid = id;
            }
        }
    }
}
//Now mxid has the ID of the instance with the highest aggro
//It has a line of sight and is within range.

//I'm not sure how it will tie into the below code yet
if collision_circle(x, y, 400, player, 0, 1) and not collision_line(x, y, player.x, player.y, nopass, 0, 1)
{

    mp_potential_step(player.x, player.y, 4, solid)
}
else mp_potential_step(random(x), random(y), 2, checkall);