Constrained elements following mouse movement

Fraternal greetings Javascript comrades. Here's a tricky one. Can
anyone please tell me how I can make a div slide up and down within
another div depending on the user's mouse movements within the
container div? Without no click events, just movement whenever the
cursor is over the container?

Basically I'm trying to copy the excellent Perspective Tabs plugin for
Mootools http://people.cs.uchicago.edu/~mewel...ding_tabs.html -
the vertical version of it is unfortunately all messed up in IE7.

The vertical version slides a vertical stack of divs up and down
within a visible "window" formed by a containing div, depending on how
you move your mouse. Clicking on one of the divs makes content appear
in another div - I can pretty much to that with Mootools, but it's
following mouse movement that has me flummoxed.

Thank you and goodnight.

Aethaelwaerd