IPInstaller is right on the money. I would add that rather than 3 hunt groups (sounds like you're doing all ring) I'd use just 1. Set to linear. First member is ext list with users A + B, second member is ext list with A, B, C + D, third has A, B, C, D, E + F. Then repeat third list several more times (otherwise unanswered calls will restart at first again). This also gives you the advantage of going right to second or third group if everyone in first is busy. Also simplifies announcement process if you're using them, especially if you deliver wait time/queue position in announcements.