Ungrouping a Conversation in Mail

I have conversations turned on in Mail. However, it is auto-grouping messages that don't go together. (In this case, the messages have the same subject, the generic word "Question." Besides both being in my Mail, the two messages don't have anything to do with one another.)

Does anyone know of a way to ungroup these messages so they go into different conversations? If not, there needs to be some way to tell Mail to group or ungroup messages that it doesn't guess correctly on.