Not knowing the application's particular's, the only thing that I can think of is to build an analog hunt group
FND and HTA to the next phone set in the group and have the last phone in the group point to the first phone in the group. Only one phone will ring at a time.
Drawback - if phones are not busy, then each phone will ring 4 times until the caller reached an attended phone.
Hope this helps.
On the otherhand, if you used digital phones, you could solve this easily with an ACD group.
Rick