Guide words?

["David A. Wheeler" <dwheeler@dwheeler.com>]

Many dictionaries and encyclopedias have "guide words"
in a header or footer that show the words that begin
and end the page.  It's not clear how to do that in this
format.

What I'd LIKE to be able to do is highlight each keyword
with a style like 'Keyword'.  That style would automatically
bold it, set a field ('Current-Word'), etc.
Then in the header, say something like:

LHS: (field-value-at-the-end-of-the-first-line-of-page 'Current-Word')
Center: (page #)
RHS: (field-value-at-the-end-of-the-page 'Current-Word')

--- David A. Wheeler