Make a url link to text file...?

so i have a flash file and in it, it imports a text file from my server and displays the text

heres my code:

var man_laws:LoadVars = new LoadVars();
man_laws.onData = function(src:String):Void  {
    if (src != undefined) {
        my_txt.text = src;
    } else {
        my_txt.text = "Unable to load external file.";
    }
};
man_laws.load("http://mysite.com/ml.txt");

theres the code i have that gets the info on the text file and displays it

no what i would like to do is somethin like that
when i embed the file, i can put a url to a text file in the embed:

http://mysite.com/test.swf?url=http://mysite.com/test.txt

i would like to be able to do that
but if it cant find that text file, then it defaults to the “http://mysite.com/ml.txt” file

do you know how to do that?
thanx for your help