Multiple mirrors for apt-get

[Bob Alexander <bob@ngi.it>]

From times to times (in the last 30 minutes for instance) my chosen apt 
source (in my case currently ftp.de.debian.org) will not respond.

What I do is to manually edit the sources file and temporarily use 
another mirror.

Is there a trick to tell apt that after a timeout it should look to a 
second fallback server ?

TIA,
Bob