Preheat oven to 300 degrees F. Measure out 1 cup of dry cake mix; set aside. In a large mixing bowl, stir together remaining dry cake mix, 1 egg, and oil (mixture will be crumbly). Press crust mixture evenly into bottom and of the way up the sides of a greased 13"x9"x2" pan. (I just put it on the bottom.) In the same bowl, blend cream cheese and sugar together. Add 3 eggs and reserved cake mix; beat 1 minute at medium speed. At low speed gradually add milk, lemon juice, and vanilla; mix until smooth. Pour into crumb crust. Bake at 300 degrees F for 45 to 55 minutes, or until center is firm. Cool to room temperature. Spoon pie filling over cheesecake; cover and chill 1 hour before serving. Store in refrigerator. Baked cheesecake can be frozen with a covering of foil. cook's notes You can use a springform pan if desired. Increase cooking time to 1 hour 10 minutes (or until center is almost firm).