Preheat oven to 350. Prepare a 9" pie pan with cooking spray and flour; set aside. To prepare crust, combine graham cracker crumbs and oil in a small mixing bowl. Press into prepared pan. Bake for 10 minutes. To prepare filling, combine vanilla yogurt and whipped topping in a mixing bowl until well blended. Mix 1 cup crushed malted milk balls into yogurt mixture. Spoon into prebaked pie crust. Top with remaining malted milk balls. Freeze 4 hours or until firm.