[Exim] Using /etc/group as additional alias file?

I'd like to use Unix groups defined in /etc/group as an additional
source of aliases, i.e. exim should first check local parts against
/etc/aliases and /etc/group for possible expansions and then try to
deliver to local users.

However, due to the passwords and group IDs in the 2nd and 3rd column,
the format of /etc/group is not exactly what exim expects from an alias
file. I couldn't find an aliasfile option to teach exim the new format.
Is this possible at all?

I know that I could use a little script to generate a proper alias file
from /etc/group, but I hate duplicating information, so I'd like to
avoid that solution if possible. BTW, I'm using Exim 3.03 if that
mattters.

Thanks,
Martin
--
Martin Buck
Ascom Systec AG
Applicable Research & Technology
Phone: +41-62-889-5292, Fax: -5290