Slice one banana and put in bottom of piecrust. In mixer bowl, mix all remaining ingredients except bananas and topping. Mix on low speed until well blended, Add 1/2 of a 12 ounce carton of whipped topping to mixture. Beat on low speed until just mixed. Put 1/3 of the mixture on top of the sliced bananas. Slice second banana and put on top of the mixture. Put 1/2 of the remaining mixture on top of the sliced bananas. Slice remaining banana and put on top of mixture. Put all of the remaining mixture on top of the last banana. Top with the last of the whipped topping. Refrigerate for at least 3 hours or until firm.