It would be a stupid decision.
You never, ever move up to take a running back. They are a dime a dozen, and you even have a proven one already with Barber.
I mean, just look at us with Pierre Thomas, or look at Ryan Grant with Green Bay, or NY Giants, or Tampa Bay with Ernest Graham, etc.
The Cowboys have an aging Glenn, TO isn't going to be around forever, and they have secondary issues and could use upgrading on the OL, all positions which they could get a great guy where they are drafting at.
I don't understand this move at all.