Tealamutt - If the horse is lying there and is not thrashing about, then they are comfortable and you can just let them be. It's pretty much the same thing as standing there - there is no chance of the gut twisting.
They get into trouble when they roll - that's when you walk them to keep them from going down and to try to jiggle out any gas that may be causing the problem.
Just because the horse is colicking doesn't mean you have to walk them til their feet fall off - you want them to stay comfortable until the vet gets there, so you give banamine and monitor. Walking them if necessary to prevent them from rolling. But if they are lying there comfortably then it's probably not a very severe case.