I have searched for an answer and apologize if it already exists...

I am trying to replace words in a document with a field after I have already
composed the doc. For example, assume I have written a book about apples,
and later decide that I want to substitute the word "apple" with a field,
whcih of course can carry the value "apple" or any other fruit I choose to
define.

Once my book has been written with thousands of literal "apple" words
throughout, what's the best way to replace those instances with my new field?

I have tried to force find/replace to do this but without success. Thanks
to anyone who helps out.

Mike