Smash blueberries using a food processor. Strain, saving juice. Mix cake mix, Jello, eggs, oil, water and 1/2 cup smashed blueberries. Bake at 350 degrees for 25-30 minutes until a toothpick comes out clean. Let cool completely. Mix powdered sugar, butter and 1/2 cup reserved blueberry juice for frosting. Spread frosting on cooled cake.