Ring group strategy

I have a requirement for a “round robin” style ring strategy in my ring groups. Like “hunt” but starting the hunt on a different extension each time.

e.g. with four extensions in a ring group, A B C and D:

First call: ring A then B then C then D
Second call: ring B then C then D then A
Third call: ring C then D then A then B
etc.

Any idea how difficult this would be to implement?

Aled Morris