Prepare piecrusts according to package directions. Fit 1 piecrust into a 9-inch pieplate.
Stir together no-calorie sweetener, flour, and cinnamon. Sprinkle one-fourth of flour mixture over sliced apples, tossing to coat.
Spoon apple mixture into prepared pieplate; dot with butter. Sprinkle with remaining flour mixture.
Place remaining piecrust over apple mixture, crimping edges. Lightly brush crust with milk, and place pie on a baking sheet.
Bake on lowest rack at 350° for 50 to 55 minutes or until golden. Serve pie warm with sugar-free ice cream or thawed lite frozen whipped topping.
* 5 Granny Smith apples and 1 Golden Delicious apple may be substituted for Cortland apples.