Layer bottom of 9x13 dish with graham crackers (leave whole, do not crush). In a bowl, mix pudding, milk and cool whip until thick. Pour 1/2 of the pudding mixture over graham crackers. Put another layer of graham crackers over pudding. Then add remainder of pudding mixture. Add final layer of graham crackers. Soften icing in microwave for 1 1/2 minutes and pour over top of graham crackers. Chill at least 3-4 hours.