What you mean under "lens wheel"?
Existing topic:
http://www.personal-view.com/talks/discussion/499/20mm-pancake-afs
http://www.personal-view.com/talks/discussion/297/20mm-f1.7-af-in-video/p1
That ring controls the motor that is inside the lens. It is highly unlikely that it could do anything else without some serious hardware modifications, that could be performed only by some runaway team of Panasonic engineers that happen to have hijacked a lens factory.
But i suppose that you can always attach something over the lens, like key chain or dog leash, maybe grocery bag or something, perhaps even a small collapsible umbrella!
No. A function assignment isn´t possible (to the lens ring).
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