How to use the mouse scrollwheel to trigger a macro/service?
One of the best apps that I have found that can do that is BetterTouchTool. It is free for MacOS 10.6+ It allows you to create links from all kinds of gestures, and button combinations. It works for the Magic Mouse, Normal Mice, Touchpads, Apple Remote, Siri Remote, Etc.
I was unable to get the cmd+scroll alone to work, but cmd+shift+scroll works great. To get it working: Install from https://www.boastr.net/ then open the app preferences and go to &quot;Normal Mice&quot; for gestures. &quot;Add New Button&quot; then Hold down the shift key as you scroll over the action area. (3) Make sure to check the Shift and the Cmd boxes.
Add a &quot;Custom Shortcut&quot; of + or -
You will have to create an entry for scrolling up and scrolling down separately.

Limiting The shortcut:
In the left panel &quot;Select Application&quot; you can have the Shortcut usable Globally or only apply if a specific app is active, ie. only work if you are in Chrome.
Advanced -- if you only want the shortcut to apply to a specific app you can setup a &quot;Predefined Action&quot; -&gt; &quot;Send Shortcut to Specific App&quot; You can then Choose an app that receives the + or -