"Split a String (movieClip Path)!"

Hi all you flashers.
I have a problem here that I’m trying to solve but with no sucess.
I made a dynamic xml picture thumbs and now I want it to show a bigger picture when pressing the right thumb.
So when I press the picture thumb goes like this:

var conversio:String= this; // I only made like this because the thumbs are duplicated MovieClips Ex: duplicateMovieClip(this,"container_mc"+i,i)
trace(conversio); //gives me "_level0.instance1.scrollMovie.container_mc0" where "0" is thenumber of the clip
//Now when I do this, it doesn't work
var split:Array = conversio.split("_");

 for (var i = 0; i<split.length; i++) {
     //clip = split*; my objective is to know the movieClip NUmber "container_mc0"

I someone knows another way to show a big picture by pressing the thumb, hey I’m open to new ideas