Such a "synch" is potentially very complex to pull off. If you are willing to spend the $$, there are third party synch tools available for this. SeedCode and 360Works are two such providers that I can recall and they are not the only sources at this time.
But you can also give your part time worker a password that does not allow them to delete records. You can host the database from your copy of FileMaker and your helper can use a different licensed copy of FileMaker to access the hosted database as a client--thus enabling you both to edit records at the same time in the same copy of the file. This avoids any need to "synch" different copies of your file.