Oops — my bad. It's not a script, it's a plugin.
What I need to do is simple. At the bottom of, for instance, page 96 of the 198-page catalogue I need to break the story so that I can save the catalogue in two parts: white pages part 1 and white pages part 2. With all the other stuff in 44 pages (called blue pages), I can then set up a book: white pages part 1, blue pages, white pages part 2, and that deals with page numbering so that I can export each part as a PDF for the printer.
In fact it's already at the printer but I had to Cut (from the top of p97) and Paste into a new document. I suppose that isn't so bad but I'd just like to be able to do it with a simple click (as before with the CleverText plugin from aextra software).