Just for your info please check this term on Answers.com. It has a lot of info on it. Here is a small abstract from it (in italics).
The sphincter of ampulla or sphincter of Oddi is a muscular valve that controls the flow of digestive juices (bile and pancreatic juice) through the ampulla of Vater into the second part of the duodenum. The sphincter of Oddi is relaxed by the hormone Cholecystokinin (CCK) via vasoactive intestinal polypeptide (VIP).