extension list ring time

Hello!
I have a call group whith 3 extension in it, and there is an option "Ring Time". Everything works perfect, but i want more. ))

I want to set ring time for each extension. May be not for each, but at least increase ring time for one of them.

First extension is secretary, this extension must ring 3 sec, second - managers, must ring 30 sec, and if nobody picked up, after 33 sec this call must add third extension.

Ring Strategy: memoryhunt.

If I use forward call to "Destination if no answer", I have delay between reconnections.

Thanks!