Prepare Cake batter and bake as directed on package for 13 x 9 -inch pan.  Cool cake in pan 15 minutes. Pierce cake with large fork at 1/2-inch intervals.  Add boiling water to gelatin mix in small bowl; stir 2 minutes until completely dissolved.  Stir in cold water; pour over cake.  Refrigerate 3 hours.  Frost cake with cool whip.  Refrigerate 1 hour.