Combine cookie crumbs and margarine in a small bowl, and stir well. Press into bottom and 1 inch up the sides of a 9-inch pieplate; freeze 1 hour.
Spread Banana-Nut Ice Milk into prepared crust, and freeze for 1 hour or until firm.
Place 3/4 cup whipped topping in a freezer-safe bowl, and set aside. Place caramels in a small saucepan; cook over medium-low heat until melted and smooth, stirring constantly. Remove from heat; stir in remaining 1/2 cup whipped topping. Fold caramel mixture into the 3/4 cup whipped topping; cover and freeze 30 minutes. Spread caramel mixture over pie; freeze 1 hour or up to 3 days. To serve, place chocolate sauce in a zip-top heavy-duty plastic bag, and seal bag. Snip a tiny corner off bag; drizzle chocolate over plate and pie.