only way is to hash it so that it is meaningless. But if users also have access to the hashing code they can reverse engineer it.
With regards the table, set the input mask property to password - which replaces the text with large dots (it does on my machine anyway). However a user can easily remove the format, so you are back to hashing.
Hashing is the alpha equivalent of shuffling a pack of cards with one or more additional packs thrown in and has been covered many times and there are many solutions, so best to google something like 'vba hashing' and find a solution that works for you.
