So, in addition to applying the editing restrictions discussed in your other thread (
https://www.msofficeforums.com/word-...able-word.html), you want each authorised user to supply a different password to validate their input? As discussed in the other thread, you would need a content control in the table and an on-entry macro that triggers the password check (you could even have the entire table within the content control). It also means the passwords would have to be stored in the macro itself (and that means both you and the users will know them, but your users can't change them)... not particularly secure.
I wonder whether this is overkill. If you're already restricting access, the relevant content control can be used to automatically retrieve the digital signature based on the username - without the need for any passwords.