I need to add a row (keeping the format above) immediately following a 'true'
statement. I.e. if column k="C","R","RB" or "P", add row replacing
"C","R","RB" or "P" with "S".

I am trying to develop a spreadsheet to handling our invoicing for a
specific customer. Each of the above product codes needs an "S" line (for
shipping cost)