Custom dictionary to highlight words listed therein only?

[szachraj]

How to make Word highlight/underscore words that are listed in a custom dictionary and not words outside of it?

[macropod]

Word can't do that automatically; what would be required is a macro that reads the custom dictionary then uses Find/Replace to highlight all the words in your document that match the custom dictionary entries.

[Charles Kenyon]

You could approach this by putting your list into an exclude dictionary. Activate the exclude dictionary after completing a regular spell-check. It will not select or highlight the words in the exclude dictionary, but it would mark them as misspellings.

Mastering the Spelling Checker