No, you're over-complicating it, it's really easy.
You just map the two commands mentioned by Shinjo to buttons, so that you have one button fur "up" and one for "down".
To get the throttle from cutoff to flight idle you press your "up" button 3 times, to get back to cutoff you press "down" 3 times. From low idle to cutoff it's, think you know it alreay, "down" button pressed 1 time.
Hope that was comprehensible.