If your mouse has a scroll wheel, you can configure Wave Editor to respond exactly as you need it to. You set this up using the Scroll Wheel Actions window, found in the menubar at Wave Editor > Scroll Wheel Actions.
To create a new Scroll Wheel Action, click the "+" button in the lower left corner of the panel, select the Axis, key modifier(s), and an Action. Enable the "Reverse" checkbox to reverse the Action behavior.
To remove a Scroll Wheel Action, select it in the list and click the "-" button in the lower left corner of the panel.