Hi, ... you can use Usernames or Groups. Here's an example with an existing Directory:

[www] path = /var/www comment = "Das Verzeichnis für Websites" valid users = User1, User2, @Usergruppe write list = User1, User2, @Usergruppe read only = yes force group = www create mask = 770

uhhh looks bad ... no linefeeds .. but i think, you understand what i mean. Look in your smb.conf then you see how to format the Lines.