It's a very basic problem to which I'm not readily finding the answer in searches. I wish to apply master pages and consistently, no matter how I format the request, am notified: "one or more of the pages specified are not valid page names." So please provide an example of how the page/section names are supposed to be written for:
A 100 page book with 1 section;
A 100 page book with 2 section;
Applying master page changes to only a subsection of the book (i.e. pages 50-75).
I'm aware it's similar to "Sec1: 1-100", but not precisely that.
OK, I think maybe I'm beginning to understand waht you are doing. Are you trying to use the Pages Palette menu to Apply Master Page to a range? You would need to include the section number for both pages, like this: Sec1:1 - Sec1:100.
You can also select the pages in the palette first, then use the apply master command. That might be easier.