Inside of the binding, you could do a asp.net function to replace the value that it produces and go to your custom page. The markup should look similar to this:
<h3><a href="<%# GetGroupProfileUrl(Eval("GroupName",true)).ToString().ToLower().Replace("workgroups/marketing.aspx","Team-Up/Marketing.aspx") %>" </h3>
That should produce the correct results I would imagine. Just make sure the string you are replacing matches what the href is producing currently and you should be good.