Use for the FO's CRS?

Okay, I admit it. I am embarrased that I do not know (or remember) what the use is of the co-pilot's course setting is. I realize that it could be handy for navigating off of a 2ndary fix, or for setting a different CRS when making an approach to an airport that has shifting winds and you anticipate a missed approach to a 2nd runway, but really, what is the thought behind this? Is it there just for redundancy in case the Pilot's DUs become unavailable? It came to me as I have been contemplating what needs to be implemented in the different stages of my L45 project's construction.

Thanks for your answers, and go easy on me. Hopefully your answer(s) will job my memory.

I posted this question on Airliners.net (as it's something I'd wondered for a while) and got a great answer. Not wanting to cut and paste in case it breaks any forum rules, here's a link

http://www.airliners.net/discussions...d.main/198628/

There is an immense amount of knowledge on this forum from real airliner pilots, well worth the small fee to join and be able to post.

hope that's helpful.

Kris

EXCELLENT answer Kris, thanks a million!