Preheat oven to 350 degrees F. Grease a 9 x 13-inch pan
Peel and chop the apples into small pieces (3 small Granny Smith apples make about 3 cups). Toss the apples with the sugar, cinnamon, and flour. Set aside
In a medium bowl mix the spice cake mix, 1/2 cup evaporated milk,, and melted butter. Spread the mixture into the bottom of the prepared pan.
In a small saucepan heat the caramel bits and the 1/3 cup of evaporated milk. Heat over medium-low heat until melted. Stirring occasionally. Set aside.
Sprinkle the apples over the cake mix mixture. Drizzle the caramel over the apples. Sprinkle the chopped walnuts over the caramel.
Place the bars into the preheated oven. Bake 35 to 37 minutes or until when a wooden pick is inserted comes out clean.
Cool on a cooling rack.