MUI - question about grouping

[Comperio]

This seems like it would be very simple, but I can't seem to get it to work:

I have a custom InstallOptions page that has 2 groups of 2 radio buttons (4 radio buttons total). Each group is placed within it's own GroupBox control.

I'm trying to get the 2 groups to work independently--in other words, allow the user to pick one radio button from Group 1 and 1 radio button from group 2.

I know that I probably just need to use the GROUP flag in the InstallOptions INI but I can't seem to get it to work. The InstallOptions help seems a little vague and I've been unable to find any good examples.

Does someone out there perhaps have a small example of how to properly format the install options INI file?
Thanks!