Have you looked at the shipping example called User Interface Event Example.vi? It is a queue driven state machine that handles both pull down menus and front panel controls. If you have looked at it, what other functionality do you need?
Also, there is new toolkit available for LabVIEW 7 Express called the State Diagram Toolkit that greatly simplifies the creation and management of large applications. You can find more information on the toolkit at http://sine.ni.com/apps/we/nioc.vp?cid=12314〈=US . This is a great toolkit if upg rading is an option.