Well, I thought somebody already did it and could tell us how it works, surprised to be the first on this.
I have found instructions from Goole here: https://www.google.com/support/googleanalytics/bin/answer.py?answer=55576, but it is not that easy as each test you do takes 24 hours to wait for the results.
I think I will use the "after save message" to insert the tracking code, but I may be completely wrong. To be followed...
Franco