samba - Dec 2001 - %G

I use samba 2.2.2 and linux MDK8.1.
I would like to use multiple configuration file (smb.conf) depending on
the group of the user connected.
so i use the include directive like this:
include = /etc/smb.conf.%G

but samba don't know %G (log file says that)
but with the previous version of samba it worked.

I've tried with other parameters, %a for the client OS, %U for the user
and it works.

Does anyone know why ?