Attachmovie depth help

1

I was making a small animation maybe for forums and stuff just wanted to see if i cud do it when i had some problems. What i want to happen (don’t ask why) is to have these random movie clips from the library to come on stage from the far right side and to move over to the left and be deleted, but have the movie clips being moved, deleted, and loaded continuously. The problems i’m having are that i can’t get the clips to be attached to the right side because the depth is all different. So can any1 help me with this depth problem im having. here’s the code on the first frame. I will attach the .fla file too. Thanks.

onEnterFrame = function() {
 //random number generator
 rand = Math.random()*20;
 //how many movie clips should be on the screen at once
 obstacles = 2;
 //if rand is greater than or equal to 16 load rail
 if(rand >= 16) {
  _root.attachMovie("rail", "rail1", rand)
 }
 //if rand is less than or equal to 5 load wall
 if(rand <= 5) {
  _root.attachMovie("wall", "wall1", rand)
  wall1._x = 200;
 }
}