apt with ftp proxy

[Pierre Monestie <monestie@lion-ag.de>]

Hello,
I hope it is the right place to ask this question:
I try to use apt/ftp to install the new slink. The problem is that I'm
under a firewall. I tried to set the ftp_proxy variable but it doesn't
work. In the previous version of debian I was configuring dselect like
that:

ftp site: gate (my ftp proxy server)
passive mode : y
username:anonymous@ftp.debian.org
password:monestie@lion-ag.de
debian dir /debian/
Go through an authenticated FTP proxy :n

Is there any way in the apt sources.list to give such a config? I read
the man page for it which is refering to a ftp.conf manual page which I
cannot find!!

Thanks a lot for your help. 
I really like what the Debian team is doing.
Pierre Monestie