100% of the browser window?

I’m working on a few web pages and I’ve got a navigation bar that I’ve made in flash that’s obviously a certain size, say 100 pixels tall, and it’s located inside of a div that’s right next to the main content (on the left). Anyway, the div only extends to the end of the .swf, even though I’ve specified for it to be 100% of the page. Ideally I’d like the box to extend to the bottom of the page, so that it doesn’t look awkward where it ends. Any idea’s as to how to have it cooperate?