shield user groups from each other

[mmensink]

Hi everybody,

I searched but can't seem to find it: I have several usergroups, and I don't want everybody to see everybody from different usergroups. With an individual login of a user, this doesn't give any problems because of the way share maps are constructed. BUT, if for example in Notes Station 2.1, a user wants to share a notebook with another user, ALL users become available for sharing, including 'admin', 'MySQL', 'ssods', etc. In short, even functional users, not attached to a physical person, are visible. Apart from being error-sensitive, this does not radiate professionalism.
What I am looking for is a method to keep users within their respective user group, and be invisible/unaware of user (groups) outside their group.

Hope anyone can help?
Thanks!