I am trying to format a 13k list of cells with one command if possible. Each cell will have data but I only want to bold certain words in that cell.

Example:

A1 John, Mary, William
B1 Robert, James, Mary
C1 Mary, John, Paul

In this example I would like to bold Mary each time in a long list

I would like to carry that format down the column 13k+ times. Is there a command that can do this