Glad it helps! It is technically possible to walk between any of the terminals at DFW (except for E, which is not accessible by foot within the secure area) without leaving the secure area. It's been a while since I've done this, but I think there are moving walkways in the connector between A and B.

In case you're not aware, the SkyLink train is the fastest link between all terminals at DFW (it's about a two-minute ride between terminals A and B). It is clearly marked throughout each terminal, and it has two stops in each terminal. Just keep an eye out for the SkyLink signs, which will direct you toward the escalators and elevators leading up to the stations.