fff89994_ation_Wheel___Beyond_the_Paper__Description
[Wedge] Zoom [Usage Steps] When you click and hold the Zoom wedge, the mouse pointer changes to the Zoom Tool. You drag the Zoom Tool upward to zoom in, or downward to zoom out. You can also press Ctrl+click to zoom in or Shift+click to zoom out. You release the mouse button to exit the Zoom Tool. [Description] 
Dynamically zoom the view.
Autodesk Design Review 2008: Full Navigation Wheel - Beyond the Paper
Description