Is cmd-option-mouse wheel possible as a trigger?

I would like to control my system volume via the mouse wheel. I have a "normal" mouse (AFAIK).

  1. I was thinking of cmd+option as modifier keys; my keyboard is an old ergonomic PC one so I don't have fn or ctrl. But in the trigger configuration area, cmd is not available. Is there some way to define what I want?

  2. I made a pair of gestures for this and just to test them out I selected Shift and Option as modifiers, but the volume doesn't change. If I turn off the modifiers, and spin the scroll wheel, the volume does change.

I'd be grateful for any help with the above two questions! Thanks :grinning: