Hey Fred,
If I understand correctly: you want the series to update occurrences upon save - but not overwrite additional data added to the occurrence manually.
This would be an extremely complicated functional logic to put together and I don't believe this can be accomplished.
We do have in-house Consultants that can look into if it's a possibility. If that's a route you want to take shoot me an e-mail and I can have you in touch with your Account Manager.
-- Mortaza