Pointing RH9 project at new linked FM files without a complete rebuild

Seems simple but we can't figure out how to "point" an existing RH9 project with linked FM files to a new set of FM files. 

As a background, our practice is that with each new version, we copy all FM files to a new directory and create a new version of the FM book and files.  Hence, after this process our RoboHelp file points at the old files and we'd like to easily update this without completely rebuilding the project and all settings.