Conditional Formatting Background On Continuous Form

I have a continuous form in my Access 2013 application.  Each line is pre-populated with values (Year, Principal, Interest, Penalty, Lien Fess and Atty Fees) from the bound record.  The bound fields are locked, no entry permissable.
Each line also has bound fields (NewPrincipal, NewInterest, etc..) pre-populated with the same values.

The user is permitted to change any of the bound values.

If the user changes any values in the 'New' fields I would like the background of that line of the continuous to be yellow.  There can be many lines on the continuous form and not all will be changed.  By making the background of any changed records yellow it would be easier for the users to keep track of which records had already been updated.