GL Daily Rates - Limit User access to only one Currency and Type

I need to restrict a user  to only update currency daily exchange rates made form any currency to the RUB for a Central Bank Rate type.  This user must be prevented from updating any other rate data.I created a unique responsibility and now need to know the best method to restrict access, Profile validation for the form LOV or Value Sets, or another method.  We have GRC, but would like a standard application solution.
We are running 12.1.3