You can use back up utilities to make back up copies of your file, provided that you do not make back up copies of the file while it is still open. You can set up a script that uses save a copy as, to save copies of your hosted file when run from the host computer and then backup utilities can make backups of this back up copy.
Perfect - great solution - thank you
There are two commonly used backup utilities.
Free for cloning $28 to unlock all features
Carbon Copy Cloner http://www.bombich.com/
One of these in addition to Time Machine would be best.
Time Machine's limitations and how to overcome them
Better backups with Time Machine
Thank you - very informative