How can I go back and forth between Word and FrameMaker

I have a client who has all their documentation in FrameMaker, but needs to export to MS Word to distribute files for editing by various parties. Once edited, my client needs to bring the updated text back into Frame, ideally without having to re-format the entire file. It was suggested that RoboHelp 10 might work, but they are using unstructured FrameMaker.

Any advice would be greatly appreciated.

Thanks!