ActionScript 3 :: 100 MovieClips Of Different Sizes - Dynamically Generating Grid

Our client has tasked to dynamically generate grids with different size boxes. The grid should not have defined edges, but each movieclip should have a certain defined border. I'm pretty new to AS3 still, but can handle pretty much everything besides this sort of giant math problem. Here's a simple layout of what I'm looking for on a much smaller scale: [URL].

I can almost emulate this, but sometimes my boxes will overlap, and that's a dealbreaker. If I start hitTesting it works up until I try it with 55+ movieclips, then I fear that the script could freeze. Here's the code that works, but may freeze at times. How can I optimize this so that stack overflow errors can't happen?

package {
import flash.display.MovieClip;
import flash.display.Sprite;
import flash.utils.getDefinitionByName;
public class box_builder extends MovieClip {
private var _path:MovieClip;
[Code] .....