In a CHM file, an end user can right-click on a chapter /
book title in the Table of Contents and select Print, then choose
to print all topics within the chapter. Could that be what you are
looking for?
In my experience, by the way, I have found that trying to
print whole chapters (or multiple topics) at a time ends in
not-good-ness. I don't know the threshhold, but at some point my
printers run out of memory or something, and just start spewing
gibberish. I always end up printing one topic at a time. Wouldn't
say my topics are particularly involved - rarely more than a screen
length, although many have one or two tables and maybe a screen
shot.
So be prepared, I guess, for the possibility that whatever
you figure out as a way to print multiple topics, you can still run
up against printer issues that send you back to printing one topic
at a time.
Good luck.