If I understand you correctly, you're saying that each chapter of your manual is a discrete Word document.
If that's the case, then opening the document for a chapter and querying its BuiltInDocumentProperties will give you the number of pages in that document, and hence, in that chapter:

ActiveDocument.BuiltInDocumentProperties("Number of pages")

hth,

-Peter

It is possible, but how you do it depends on exactly what you want included
in the List of Effective pages. I recently did an automation project on this
for an airline, where they wanted the revision level for each page listed.