Prepare and bake cake in a 9x13 inch baking pan, according to package directions. Remove cake from oven. Let cool 30 minutes. Using the back of a wooden spoon, poke holes all over the cake. Mix together jello powder and boiling water until jello dissolves. Carefully pour mixture evenly over the top of cake. Cover and place in fridge to chill for a few hours. When ready to serve, spread cool whip evenly over the top of cake. Cut in pieces and serve with sliced strawberries. Enjoy!