Yes there is.
http://www.ubbwiki.com/wiki/view/82/groups.html
read the section editing a group.
FYI.
After you make the change the members will need to make one more post before they get the change.
Meaning you set a group2 to be at 100 posts and a user currently has 150 posts. they don't get promoted till after they make post 151 after you make the changes in the control panel.

Blue Man Group
There is no such thing as stupid questions. Just stupid answers