If you ever have the urge to capture a specific key pressed in Flex or AS3 in general, there is an excellent list of the keycodes, and costants you can use to represent them in your code here: http://livedocs.adobe.com/flash/9.0/ActionScriptLangRefV3/flash/ui/Keyboard.html
You can use them statically(without instantiating an object) like so:
trace(Keyboard.TAB); // 9