I have a large dictionary file. The headwords and parts of speech (noun, verb, etc.) have the same custom style. How do I change the parts of speach to a different custom style without changing the style of the headwords?

headword1 noun definition
headword2 noun definition
headword3 noun definition
headword4 verb definition
headword5 verb definition

I can use Find to search for "noun", "verb" etc., but how do I use Replace to change to a custom style. In the Replace window, under More>Replace>Format>Style..., custom styles are not listed.