[ElaineM]

If I were in your situation I might try changing my diet temporarily. I would reduce fat in the diet, and eat less of the whole grain foods and more white grains temporarily. I might try a diet similiar to what a person with the flu might eat and slowly add back the foods I took out of my diet one by one until I could eat normally without problems.
Even if Tykerb is the culprit one can learn to eat healthy without too much diarrhea. You can try to reduce the Tykerb dose temporarily for a few days and see if that makes a difference. You will still be getting some benefit from the Tykerb. You can add back a little Tykerb every few days until you reach the normal dose and see if that helps. Just make sure you tell your doctor what you are doing.
Rich is right about probiotics. They help straighten things out in the gastrointestinal system. If you can't get the medication he suggested eat more good quality yoghurt or other foods with the same healthy bacteria that yoghurt or the probiotic medication has.