How NOT to import selected files in FM book to RH?

I have some files in my FrameMaker book, that I do not wish to include in my RoboHelp help system.

Any ideas on how to handle this the best?

- Is the best idea just to create a new book in FrameMaker, where I have deleted these files?

- Or is it possible somehow to apply conditional text "not for RoboHelp" on file level?

... Suggestions are very welcome ...