Make the red velvet cake according to the package directions and allow the cake to cool. Using a serrated knife, cut the cake into one-inch square pieces and line the bottom of the trifle bowl with a third of the cake squares.
Next prepare the frosting. In a large bowl, beat the pudding mix, milk, and sugar with a whisk for about two minutes. Then, fold in Cool Whip.
Layer a third of the blueberries and strawberries on top of the whipped topping.
Layer another third of cake pieces on top of the berries to form a second layer of cake. Add more frosting and more berries.
Repeat this step one final time. Top everything off with the rest of your berries to complete the trifle.
Notes
*You will also need the ingredients required to make the boxed cake mix. Baked your red velvet cakes according to the package directions.