Grease and flour two 9-inch cake pans and set aside.
Mix together cake mix, milk, oil, eggs, pumpkin pie spice and only 1 cup of the pumpkin.
Pour in cake pans equally and bake at 350 degrees for 25 minutes or until done. Let cool for 10 minutes and remove from cake pans onto cooling rack. Cool completely and cut layers in half giving you four layers.
In a mixing bowl, mix remaining pumpkin and cream cheese. Continue mixing adding powdered sugar, pumpkin pie spices and Cool Whip; mix until creamy and fluffy. Stack cake layers with this mixture between each layer, then ice the sides. Do not ice top of cake! Pour caramel sauce on top layer and let it drizzle down sides of cake.