Accessing dynamic added objects

I’m building an videoplayer with XML list.
I dynamically add multiple instances of a movieclip from the library (to hold the contents) to a movieclip called Holder wich is on the stage.
The instances are named Disp0 to Disp5.
So far it works out.

But how do I access these instances, my thought was:
Holder.Disp0
Why isn’t this working?