SQL & Forum Thread

I've created a user forum and need to have the ability for users to search messages. I can easily search each each message for the request criteria.

SELECT ForumMessages.Message
FROM ForumMessages
WHERE (((ForumMessages.Message) Like '*br*'));

However I do not need each message, what I need is each thread that has the search criteria. My question is how do I take only the top thread when doing the 'Like' query. Would a sub query work?

SELECT ForumMessages.Message
FROM ForumMessages
WHERE ID IN (SELECT IIF(ParentID=0,ID,ParentID) FROM ForumMessages WHERE ForumMessages.Message Like '*br*');