In a medium bowl, thoroughly blend the pudding mix, whipped topping, and milk.
Arrange a single layer of graham cracker squares in the bottom of a 13x9 inch baking pan. Evenly spread half of the pudding mixture over the crackers. Top with another layer of crackers and the remaining pudding mixture. Top with a final layer of graham crackers.
Spread the frosting over the whole cake up to the edges of the pan. Cover, and chill at least 4 hours before serving.