Prepare cake mix according to package directions. Bake at 350 degrees F for about 30 minutes. Cool cake completely.
Bring 1 cup of water to a boil. Pour Jell-O into a small bowl. Pour boiling water and stir until dissolved. With a dinner fork, puncture the top of the cake with holes. Pour half to most of the Jell-O mixture into the holes. Using all of it may cause the cake to become too wet. The result will be a swirling effect in the cake.
In a medium mixing bowl pour whipping cream, sugar and vanilla. Beat well until thickened and peaks form. Spoon onto cake and spread like frosting. Chill a few hours and serve.