I am new to both window hooks and Windows 8 metro apps..
I would like to develop a background service/process that:
It is not possible to hook Windows or intercept the launching of a Metro style app from within a Metro style app itself. While it may be possible to do so with a service installed on the machine in a classic way, doing so would be totally undocumented and unsupported. You would have to reverse-engineer the app launching process to have any chance at making it work.