Something

function loadMyText(evt)
{
    var _loc2 = new LoadVars();
    _loc2.load("texto.txt");
    _loc2.onLoad = function (success)
    {
        if (success)
        {
            my_txt.htmlText = this.content;
        }
        else
        {
            trace ("Could not load text file.");
        } // end else if
    };
} // End of the function
loadMyText();
var flash_css = new TextField.StyleSheet();
flash_css.load("estilo.css");
flash_css.onLoad = function (success)
{
    if (success)
    {
        my_txt.styleSheet = flash_css;
    }
    else
    {
        trace ("Could not load CSS file.");
    } // end else if
};