Saving variable to text file in standalone app

I am using flash MX and am trying to do the following:
I have a dynamic input text field, and below it a "submit" button. When the user inputs some text and clicks "submit" I want this text to be sent to and saved in an external .txt file. This is all it has to do. I know it has something to do with variables - remember that this is for a CD application (eg standalone, no server interaction) so I don't think I can use back-end scripting. Please help!

Thx.

If you find out how to do this I'd love to know

Haven't had any luck so far! Seems like this is asking the impossible of flash... Are you working on a similar application? Any luck?