Doug, send me an IM later and I can walk you through it.
Yes, the code I gave you, modified from the original reply, designates cells A1 and A2 on the worksheet itself as identifying both the column letter you wish and the replacement text you wish respectively.
If you your code is running and you paste new code into the running module, you will get the "reset current project" error, so it is always a good idea to stop your current macro before making changes.
You said you wanted to add an S to a column, that was provided, then I made it specific to a column (H) which you could have changed to work as well, and then you wanted to have it be changeable, so that was provided.
If there is a not clear explanation of exactly what you want the code to do, it is more difficult to provide an adequate response, particularly if you are unable to make necessary modifications to the code you get to more suitable.
The more specific you are, the more specific code might be able to have provided.