I don't know of any options to have the deskphone ring X number of times, then ring a cell X number of rings, and then go to voice mail. You can forward a call to a cell phone after a certain number of rings but the call will stay with the cell phone rather than pulling back to the Mitel voice mail. If that is acceptable, that is probably your best bet. It sounds like right now you are specify the total number of rings the call will have in a ring group before it goes to voice mail. In my experience, there is always a delay of 2-4 rings on the deskphone before the call can be connected to a cell phone in the ring group. The call continues to ring the desk phone but will also ring on the cell phone. The cell phone stops ringing when the call is sent off to voice mail based on the number of rings in COS. Unfortunately there is way to much variability in the timing of connecting the call to a cell phone to decisively say, it will ring X number of times on the desk phone then go to the cell phone for X rings. Even with 6 total rings before voice mail in my ring group, I still get calls every once in while that only give me a half ring on my cell. YMMV.
