You should be able to do that with some creative javascripting in the template editor (DAXEXIT.EXE).

The section to look for under the Start Page tab is:

<!--[Group(title,overview)]-->
<!--[GroupPageLink]--><!--[GroupField]-->????<!--[/GroupField]--><!--[/GroupPageLink]-->
<!--[/Group]-->

You need to pass these parameters to a javascript and then have the javascript create the HTML output in three columns.