samba - Feb 2008 - Groups authentication?

Hi,

Is it possible to use group authentication instead of user/share
authentication?

I did create a very basic share on a test server and it allows everyone.
I would like to create a samba group on the server and only give access
to the users in that group. Can I do that?

I'm using Samba 3.0.25b on a CentOS 5 server.

Thanks!

Simon