Email address depending on date-can I put it in the preferences?

Ideally I'd like to be able to have email addresses that relate to the 
current date (e.g. [email protected]) so that I can post 
to usenet with an address that's valid for a few days incase someone 
wants to email me, but times out so is (relativley) useless for spammers.

Server side it's no problem, but it seems that recent Mozilla builds 
won't accept arbitrary code in user.js/prefs.js - can anyone think of a 
work around? I generally reboot the computer daily so it won't matter if 
it's only read each time mozilla starts. The best I can think of so far 
is a cron job on linux to change user.js, and some kind of equivalent on 
windows. Is there any better solution?

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