As of IE6 I believe you cannot customize the scroll bar using those properties. The Chris Coyier article linked to above goes into nice detail about the options for webkit proprietary css for customizing the scroll bar.
If you really want a cross browser solution that you can fully customize you're going to have to use some JS. Here is a link to a nice plugin for it called FaceScroll: http://www.dynamicdrive.com/dynamicindex11/facescroll/index.htm
