getting closer but when my laser (bullet) hits the asteroid it says can't open file.
Here is the relevant part of my code:

function remove_asteroid()
{
var boom_percent = 0;
if(event_type == EVENT_IMPACT)
{
wait (1);
ent_remove(me);
ent_remove(laser);
}
}

action asteroid()
{
ent_create("laser.mdl", vector (26000, 0, 0), laser_fire);
rock = me;
while (1)
{
c_move (my, vector(-25*time_step, 0, 0), nullvector, GLIDE); // move the fragment left
wait (1);
my.emask = (ENABLE_IMPACT); // make entity sensitive for block and entity collision
my.event = remove_asteroid;
}
}

function remove_asteroidbig ()
{
ent_morph (my, rock);
}

action asteroid_big()
{
boulder = me;
while (1)
{
c_move (my, vector(-28*time_step, 0, 0), nullvector, GLIDE); // move the fragment left
wait (1);
my.emask = (ENABLE_IMPACT); // make entity sensitive for block and entity collision
my.event = remove_asteroidbig;
}
}

thanks for the help