AS2 - Help with Random text script

Hey there.

I’m using the following script to load a random quote from a text file:

ranQuote = new LoadVars();
ranQuote.onLoad = function(success) {

if (success) {

RanNum = Math.ceil(Math.random()*25);
ran = this[“quote”+RanNum];
quote_txt.text = ran;

}
else {

quote_txt.text = “The text failed to load due to an error”;

}

}
ranQuote.load(“questions.txt”);

Is there a line or two that I can add to this that would prevent it from choosing the previously pick number again? I mean it can use it again, just not twice in a row.

Help please?

Thanks!