Perhaps an example will help you.
I modified J.D.'s Code a little bit. It differs now a little bit, but should have the same function.
Take a look here…
https://russian-dima.wixsite.com/meinewebsite/highlight-mark-some-text
EDIT: I have test the CODE right now and have recognized that the search is working, but it find always just the first word. For example, if you are searching for “and”.
“and” is given more then 1-time in the text, but it stops the search after the first search-value was found.
@J.D. how i could improve this in my code-version?