To prepare crust, combine crushed cookies, walnuts, and margarine in a mixing bowl. Press mixture firmly in the bottom of a 9" pan. Chill one hour, or until firm. Or, bake in a 350 oven for ten minutes, or until edges are brown. Cool on rack before filling. To prepare filling, combine pudding mix and milk in a mixing bowl. Mix well. Pour into crust. Chill one hour. Then, spread whipped topping over top.