Been awhile since I used Audacity. I actually use Kristal for all of my audio editing. http://kristal-audio-engine.en.softonic.com/
I am sure there is a way to set a track marker in Audacity or it might be a start and stop point. I also think there is a way to export your selection. Again I always use kristal because it is so easy to do just that by taking your track cutting where you want the start and stop and then clicking on that piece and hitting p. That will set the markers for just that piece.
I know it's possible in Audacity maybe try to find a youtube video on it.