Thanks guys, but it doesn't seem to work properly.
I can specify CMD-TAB as you both describe but in use pressing the mapped button doesn't work in the same way as pressing CMD-TAB on the keyboard. Have you tried it?
Pressing my button once switches application, whereas pressing it once on the keyboard brings up application icons.
Pressing and holding the mouse button brings up the icons but they go crazy and blink between each other really fast.
I just want to press a mouse button have have it mirror CMD-TAB pressed once, ie, have my app icons appear in the middle of the screen