insert text in columns based on maximum number of rows containg data

I have a spreadsheet that has data in 2 columns. I need to be able to determine the maximum number of rows that contain data and then insert the letter "E" in the third column of each row, and the text "CSCODE" in the 4th column of each row. I'd like to do this as a macro or some other automatic process because the file is going to be automatically manipulated by a program that has recorded keystrokes and mouse movements.

This would be done as a macro, in the VB editor, script editor??? I'm sorry, I'm not a programmer. I just need to find a way to do this.

Thanks for your patience and assistance.