Ten years after the first request, I have the answer.

In Word, select the front Opus Chords. For a flat sign, type a b. For a 7th chord, type a 7. Both these characters will be in superscript and will look right for chord notation. If you hit the ;, it will type 'omit,' which I suppose means 'Don't play anything.'

Apparently we are supposed to use Opus Chords for chords only. But I wonder how to type B-flat?