Resizing the height of a dynamic text box

i’m trying to load a text file in a dynamic text box.

i have this code which loads the text to the textbox.
text file is 3 paragraphs long. i want it all to show in the textbox
problem is, it only shows the first line. but when i tried resizing my textbox manually
it shows more text. i want the textbox to resize automatically depending on the
length of the textfile loaded.

myData = new LoadVars();
myData.onLoad = function() {
 target_mc = contentmain_mc.createEmptyMovieClip("list_mc",1); 
 news_mc = target_mc.attachMovie("newscont_mc", "newscont_mc", 1);
 news_mc.news_text.styleSheet = format; // CSS formatting
 news_mc.news_text.html = true;
 news_mc.news_text.htmlText = this.myNews;