AJAX select box dropdown update form

I have the following form with 2 selectbox drop downs:

SelectBox1

SelectBox2

WHen the user changes the selection in SelectBox1, I want SelectBox2 to be updated to contain a different set of options. I'm not sure exactly how to do this. If someone could point me in the right direction, I'd appreciate it.

Thanks

I followed the outline given at http://pullmonkey.com/2008/3/30/dynamic-select-boxes-ruby-on-rails when I wanted to do this a couple of weeks ago.

–wpd