How works Alt+Wheel in Slide edge (Blender 2.71)

I’m a new user in Blender. I used befor Cinema 4D and now I like learn modeling in Blender (some tools is better). I came across a keyboard shortcut (in Doc:2.6) Alt+Wheel in Slide edge. In manual is written that it change control edge

, but I don’t know how it works. I tried everything (Evel, Evel+Flip) but with no result (Alt+Wheel).

Thank you for answers.