How to return a list of users in a group, useing a dropdown menu to select a group.

So i'm after an live report that allows me to select the group from a drop down list and display the current users. I can return a list of people from with in a group by using the group iD but you have to know the GroupId, hence having a drop down box that displays all the groups would make life a little easier. thanks all

using SQL, Windows