1 (16 oz.) pkg. frozen black cherries, drained, reserve juice
1 lg. pkg. cherry Jello (sugar-free)
1 can crushed pineapple, drained reserve juice
1 1/2 cans Diet Coke, divided

13 x 9 inch Pyrex dish. Bring 1 can of Diet Coke to a boil. Use Coke as you liquid to dissolve your Jello. Pour Jello into a dish to jell. Combine pineapple juice, black cherry juice and Diet Coke to bring the liquid to 3 cups. Add to Jello. Add crushed pineapple and black cherries to Jello. Chill to set Jello.