firefox addon – tampering?

is there an addon which can tamper data? I know for exactly that named “Tamper Data” addon which can tamper POST and similar methods. But, my Flash application passes the request to the browser for loading xml file. I want that Flash application to load another xml file, supplied by me.
So, Tamper Data addon “catches” it when Flash attempts to get:
www.aaaa.com/file.xml
and I want an addon with which I can change that to:
www.bbbb.com/file.xml
So the flash application “thinks” it loaded the right xml file, although it got from another source
If addon of this kind exists, please tell me
Thank you very much
Answer #1
This it it:
https://addons.mozilla.org/en-US/firefox/addon/966
Answer #2
This it it:
https://addons.mozilla.org/en-US/firefox/addon/966
Thanks, but please read my first sentence once again. I said I know for exactly that named addon, and I also said it can’t do what I want
Edit: I didn’t say Tamper Data can’t do what I want it to do. Ok, now I am saying. It can just “catch” the request for the specific XML file, but can’t change the URL of that XML file, only properties which are passed to it.