Using MovieClip Variables!

Why the doesn’t the following code work:

var m = new MovieClip();
m.createTextField("txt", 1, 20,20, 100, 100);
m["txt"].text = "test";

When tracing for the text in the text field it tells me ‘undefined’. I know that if instead I do ‘var m = new MovieClip();’ I do this ‘this.createEmptyMovieClip(“m”, 20);’ it works!

However I can’t do that. I have created a method that is accessed from different movies, and I need to create the movie clip, without adding anything to scene!!

can any one tell me how I could do that?