Neat idea.
There's an applescript for the desktop version which automagically does a similar thing, it tags stalled projects and groups with -- Missing NA. Much more powerful than the built in 'Stalled' context because that also includes projects that are waiting and misses groups out altogether.
It was written by Curt Clifton, available from:
http://www.rose-hulman.edu/~clifton/....html#VerifyNA