Changing Unchanging Fonts to BOLD

Attached is a partial copy of my Sudoku puzzle (again). On this copy, 6StringJazzer wrote the code on how to the lock numbers that are applied from a solvable puzzle. This works great, but on a real Sudoku those locked numbers are highlighted in BOLD and they are also locked.. On my puzzle, I have entered a few numbers that represent parts of a solvable puzzle, and once locked they can't be written over or deleted. However, I need to for those numbers to stand out from the other numbers that you would enter. The entire puzzle is the regular font, but I want these numbers to be BOLD. Then when the Clear Puzzle has been clicked on it will return the numbers back to regular font. The Lock and Clear Puzzle Button has the macros so this is where the code should be if it can be done.

Thanks,

Jerry