Trying to trawl through the WMI/WQL MS Reference Data and the WMI Code Creator Event Classes, but can't find anything to indicate:
A) If this is possible B) How to do it
Ideally i'd like to be able to subscribe to WMI Events that are of the nature of the End User changing (UI) window (any Windows application).
You are using the wrong tool, there is not WMI classes or WMI events related to the UI of a windows application. instead you must use the Windows messages and the WinAPI.