Note that, by default, the expression will run in the context of the
"selenium" object itself, so this will refer to the Selenium object.
Use window to refer to the window of your application, e.g.
window.document.getElementById('foo')
If you need to use a locator to refer to a single element in your
application page, you can use this.browserbot.findElement("id=foo")
where "id=foo" is your locator.