Another option would be to move your entity directly, like this:
var going_down = 0;
While(ent.z > -100)
{
going_down = 1;
ent.z -= 5*time_step;
wait(1);
}
going_down = 0;
This would cause the entity to move down without checking any collision.
If your player entity has a c_move function, it will be checking collision. You could effectively turn this off while it is going down through the terrain by surrounding your c_move with an "if" statement...
if(going_down == 0)
{
c_move(ent,move_vec,abs_vec,GLIDE|ETC...) ;
}
