As we know,use Ctrl+Alt+Left/Right arrow key combination can switch between 3D desktop workspaces.This tutorial shows how to do this using mouse middle-wheel which is more convenient.
First,make sure you have installed compiz fusion and enabled 3D desktop.
Then,open CompizConfig Settings Manager in System->Preferences menu.
Select Desktop tab,and check Viewport Switcher.


Then,click on it and go into its configuration window.Click buttons after Move Next,Move Prev.Enable them and set to Button 5 and Button 4


Now,move the cursor to desktop and try the mouse-middle-wheel.When you move the cursor in windows,mouse-middle-wheel still do the function that scrolling down/up the scroll-bar.