Tagging Text in a Document (OS X)

I am looking for a method to tag portions of text in a MS word document.

I am a law student, and I do a copicious amount of research and note taking. While I have a format to most of my notes and outlines, it would be a boon if I could tag sections of notes within the document. Thus I could later search for not only a keyword but a topic. This would help ID aspects of the topic that are not best expressed in the the major point heading.

If an example helps please see my post at macworld forums: http://forums.macworld.com/thread/98042?tstart=0

Please note that I will use any text editor that will allow me to tag the text, but right now most of my notes are in Word.

Thanks,

J