I have several books with scores of individual files.
Is there a utility to automate the use of changebars?
If the files are in a book file, you can select them in the book list and then use Format > Document > Change Bars, which will open the Change Bars Properties window.
From there you can turn automatic insertion on, change the width and color, and clear them.
Yes, that's what I'm doing now and it's time consuming. Am looking for a utility that will do this from the command line.
Are you doing it from within the individual documents or by selecting multiple files in a book file? The former is tedious and donkey work, the latter goes pretty quickly.
You could create a new book file that has all of the files you need to do this to in it, and then select all the files in the book and proceed as above.
Otherwise, no, there is currently no utility I know of, command line or otherwise, that will do what you ask. You might want to check with Rick Quatro, who is one of the top FrameMaker script writers. He might be able to create a custom script for you.