Preload txt/css, how to?

i have this code that loads css formated text from a .txt file, the problem is that i get “undefined” msg when i upload it, i’m guessing this is because the text or css is not preloaded, so how do preload this, here’s my text:

// Create a new style sheet and LoadVars object
var myVars:LoadVars = new LoadVars();
var styles = new TextField.StyleSheet();
// Location of CSS and text files to load
var txt_url = “./xml/welcome.txt”;
var css_url = “./css/styles.css”;
// Load text to display and define onLoad handler
myVars.onData = function(content) {
storyText = content;
// Load CSS file and define onLoad handler:
styles.onLoad = function(ok) {
if (ok) {
// If the style sheet loaded without error,
// then assign it to the text object,
// and assign the HTML text to the text field.
styles_txt.styleSheet = styles;
styles_txt.text = storyText;