Your post seems to have nothing in particular to do with the code I posted, because that code:
1. does not process textboxes anywhere in the document; and
2. it doesn't look in any subfolders.
I didn't include either of those features because you didn't ask for them. The code in post #4 should give you an idea of how to incorporate the textbox processing into the code (some minor changes are needed for adaptation to header/footer textboxes). Sub-folder processing would entail a substantial re-write, so I don't propose to do that. That said, for the kind of code modifications needed to process sub-folders, see:
https://www.msofficeforums.com/word-vba/16209-run-macro-multiple-docx-files.html#post47785