vomiting, lethargic, won't eat

I have a 9yo Pekingese who has been vomiting for three weeks.  The vet gave us a vomiting medication (metoclopramide) which helped the first week.  The vomiting slowed and he began to eat the hamburger/chicken and rice recipe.  His bloodwork showed high calcium and high white blood cell count.  An x-ray showed no abnormalities and he showed no signs of pain during a physical.  After two weeks of on and off vomiting, he had a turn for the worst and we took him in for emergency care.  The vet admitted him and gave him iv fluids for 5 days.  They released him for the weekend and gave us prilosec and sucralfate.  He has not improved any and continues to vomit and won't eat.  Does anyone have any idea what could be causing this?  The vet says it is a mystery and we may never find out what is causing it.  The different foods we have tried to get him to eat this weekend are Cottage Cheese, Plain Yogurt, Boiled Beef and rice (even tried adding in some tuna), all attempts have failed.  Seems like even the thought of eating makes him vomit yellow bile.

[peekawho]

There is a medication called Cerenia, which is highly effective for vomitiing in dogs.  It is also expensive.

Beyond that, I have a doberman who has been vomiting now for more than a year and a half.  He's had every test known to the veterinary world, without any abnormalities.  

My dog vomits only when his stomach is very empty, though.  The Cerenia really, really helps.  He's been on it for about 3 months now.