Boil chicken in seasoned water. Debone chicken and cut in chunks. Boil spaghetti in chicken stock until tender.
Saute onion, celery and green pepper in butter. Add cream of chicken soup, Velveeta jalapeno cheese and Ro*Tel tomatoes. Cook until blended and cheese is melted. Add mushrooms and olives. Mix chicken, spaghetti, and sauce.
Put in 3-quart buttered casserole (or divide and put in two smaller). Cook at 400 degrees F for 15-30 minutes until bubbly.