Repeater control/Scrolling

I'm creating a web app that has a list of people to choose from that I want  to add to smaller groups of people. For example, I may have 100 peopple that I want to create 20 different sub groups of 5 people each. I'm thinking I want to use a repeater control with two buttons (add person, remove person) and a list box to show the list of the people in the sub group (of 5 people for example). Is that the best way to do what I want to do? Also, what container would I use to make that list scrollable in the event the list of sub groups was longer than the web web page (I don't want to have to scroll the page. That might hide the list I'm choosing people from).  Also, the reason I'm wondering if the repeater control is the best option is that it would be nice to have have columns of groups. For example, it would be nice to have 4 columns of groups for the first 4 groups. The fifth group (record) would start a new row. I bet there's a control that will do that. Is there?