drawing a selection box

[sammy]

Ok heres the deal:
When you are on your desktop, and you click and drag, the mouse draws a selection box, so that you can select multple things.

I want to be able to do that on my site.
Whenever the user clicks and holds, it turns on selection mode and as he moves the mouse, i want a box to be drawn so the user knows what he is about to select.

Any ideas?

[sde]

the browser would have to support that, which browsers don't. flash is your best bet... but that is a world of its own.