I have a spreadsheet that is going to be used in a survey. 

How can I make the cells only to return "x" regardless of what the survey taker type in. 

For instance, if I write a "w" in the cell, it should turn into an "x".

I have come to a point where I think there is an option when I protect the workbook or sheet. Because I can tell from another spreadsheet (which has this function) that it only works if the workbook is protected.

I tried to google it, but it seems as if I don't know the right keywords to find the answer.

Also, I have found a set of Vba code that I fiddle with, but I'm not sure this is correct. I don't want to attach the code as I don't want to confuse any response here.

Thank you for any help provided.