[Framers] Page X of Y, redux, except not quite

[Lin Sims]

So here I am at the new job, and we're setting up FM templates. My
coworker, who has established the house styles/layouts, had set up the old
Word template with X of Y numbering, EXCEPT

   - Page numbering for the body of the document, which is to say after all
   the front matter, (X) starts at 1.
   - Total page count (Y) does NOT include all the front matter (Cover,
   Inside Cover, RevisionHistory, TOC) or the Back Cover.

Creating X is easy-peazy, of course. But how to create Y?

[This may be something Word has over Frame, because in Word I was able to
set up a formula in the field code to calculate what Y would be and it was
all nicely automated. I've never come across something like that for Frame.
And I cannot believe I'm saying that Word does something better than Frame
...]

I've come up with two workarounds.

One is described in the Adobe forums and consists of inserting the
<$lastpagenum> building block on the virtual "last page" and then xrefing
to it from all the master pages that have X of Y in their footer frames.

The other is to set up a new variable (of Y), manually updating its value
to the last page number right before release, and importing variables to
the other files in the book.

Both of these are doable but (to me) clunky and inelegant. Is there a
better way already available? Because if not, I foresee me spending a
considerable amount of time learning javascript then extendscript in the
hopes that I can figure one out.

I like my coworker, but he does NOT make things simple for me. ;-)

-- 
Lin Sims