I'm using this demo:
http://closure-library.googlecode.com/git/closure/goog/demos/combobox.html
But I don't need user input, I've tried to disable it by this:
combobox.getInputElement().disabled = "disabled";
But it won't work in IE6/IE7 (Didn't try IE8/9), that means, in IE the disabled input field can't capture click event.
so how do I disable it cross platform?