Combine the reserved pineapple juice, cranberry juice and lemon juice in a medium saucepan. Bring to a boil. Remove from the heat. Add gelatin, stirring until it is completely dissolved. Break up the cranberry sauce with a fork. Stir into gelatin mixture. Refrigerate until the mixture begins to set. Stir in pineapple and celery. Pour into a 4 cup mold. Chill until firm. Makes 8 servings