script to dim a div's content on navbar mouse over?

first of all, how come i get the suckiest clients?

anyway, i've got this design for a website, with a vertical navigation menu on the left, i've added popup menus to each button through Fireworks with links to sections and sub-sections.
when you hover over each button you get the popup as usual.
this popup -again as usual- appears on top of all other text on the site.
what this dude wants is for the text in my main content div to dim or fade out a bit when the popup appears...
any ideas?
let me know if i'm not making sense
thank you!

here is a demo
the thing is - and don't get me wrong - that the money i'm getting for this doesn't really justify a lot of delving into lots of javascript...
i don't know how jquery and fireworks outputted javascript play well with each other...

the idea is that there will be textual content inside the grey box in the center.
the demo was done so that the client could see two different forms of navigation and they chose this one, much to my disappointment, cause it's got popups coming from practically everywhere...
anyway, the box in the centre will be a div with the image of the box as a background and so on...