I guess I don't know why that wouldn't work... You would create 2 Phone Extension Lists, one (A) with the first two people (x102 and x103 for example), then one (B) with the first two plus the third (x102, x103, and x104). In your hunt group, you put two members, Phone Extension list A and B, set the No Answer Advance timer to amount of time you want the first list to ring (15-20 seconds is common) then set the Recall timer to double the No Answer Advance timer. Set the Recall Point to the CRA that points to the mailbox (remember you can't send a hunt group directly to a mailbox).