how do i program ajax-type screens?

first of all you need to learn some HTML & javascript programming. Then all you do is type in "ajax libraries" in Yahoo search and you'll get back a number of good sites to teach you more advanced stuff.

http://search.yahoo.com/search?p=ajax+libraries&sm=Yahoo%21+Search&fr=FP-tab-web-t&toggle=1&cop=&ei=UTF-8

You can also find some useful libraries as well. Some popular ones (and my favorite ones as well) are here:

http://script.aculo.us/
http://openrico.org/rico/home.page

Depends what kind of technology you want to use to implement it.