Either example in
https://www.msofficeforums.com/word-...tml#post132696 does essentially the same thing as in the video - the 'B' version even has an extra level for you to play with. A fundamental difference is that my approach uses Content Controls, which means you don't need to apply 'filling in forms' protection for it to work.
The only valid reason for using formfields would be that you need to employ the older .doc file format instead of the newer .docx or .docm file format. If so, you will need to upload your actual document (without password protection), including the vba code you're using, so we can diagnose the problem. There is simply no way to do so from the document snippet you've posted.