Rigging question swaying to rotation

Hi, I have a rig as shown in the small video, what I want is the selected bone (at the moment a separate armature) to rotate forwards (in a staggered manner) every time the swaying bones move forward, Like copy rotation but without taking in account the backwards movement.
I have been looking into drivers but can not figure out how to do it.
Any ideas? Thanks.
vokoscreen-2020-08-12_14-49-41.mkv (120.8 KB)

What you want can’t be done with constraints and drivers alone. You would have to use something like physics or Animation Nodes.

In the end I have managed it a different way. The swaying bones were driven by a rotating rig, I used a driver to copy the rotation, then in the drivers editor I slowed it down, added a staggered modifier (just what I wanted) and inverted the rotation via “-var + 0.0” It works just as I wanted.
Sometimes posting a question makes me think a bit more!
Thanks for your answer.