Doogiet:

At the top of the BIAB screen, you will see 2 boxes that show the FIRST bar of your song and LAST bar of your song.

You said: "Oh, just bars 43 to 158. No problem. :P"

Just enter 43 as the first bar and 158 as the last bar. Then set the number of "chorus's" i.e. number of times through the song, to the number of times you want it repeated for your practice session.

I think it will then play the "intro" (bars 1-42) ONCE, then your practice bars, repeated as you have instructed. I'm not at my BIAB machine so I can't try it to confirm.

Good luck!
LLOYD S