My grand daughter has severe skin break down on her cheeks caused from her bowel movements.?

She was born with no , had to have one surgically constructed, sphincter muscles are not yet tight enough to hold in the bowel movement, has a lot of accidents. She can only drink water or milk, maybe some gatorade. No sugars. Bananas is the only fruit she can have. If we can control the bowel movements down to 1 or 2 a day the skin will slowly start to heal but it has never been 100% healed, she always some open ulcers on her skin in this area. We have tried numerous remedies from Doctors to folk remedies, home made pastes. In Sept of 2010 we had some success with "XEROFORM" petrolatum dressing with Bismuth Tibromophenate from a wound specialist, this worked for about 4 months but it has not been working as well since january. This is an open wound and causes great discomfort for our 3 year old grand daughter. Any advice you may would be greatly appreciated.