There's nothing magical about CGI's radio group shortcut. It just outputs HTML. Discover how you would accomplish the formatting you need using plain HTML, and you'll have your answer, which is to say, it's an HTML (and possibly CSS) question.

Often, when dealing with web page layouts, it's easier to mock up the site without any dynamic server-side stuff first... just you and the HTML/CSS. Once you've got it looking the way you want, you can replace key elements with dynamic content. Template modules make it easier too.