title: ExtJS Dynamically setting tab index
body: <p>How can I dynamically set a tab index in ExtJS?  I can't see anything in the docs for it, only a config option for it.  If I try to do an .apply, it still doesn't work.  I know I can probably extend the framework to support this since it is just a DOM element, but I'm sure I'm missing something simpler.  Help?</p>