Sprinkle unflavored gelatin over 2 cups cold water in a large saucepan; let stand 1 minute. Stir in sugar. Cook over low heat, stirring constantly, until gelatin and sugar dissolve. Remove from heat; stir in juices. Chill gelatin mixture 1 1/2 hours or until consistency of unbeaten egg white.
Fold apple, celery, raisins, and cashews into gelatin mixture. Pour half of mixture into an 11- x 7- x 1 1/2-inch baking dish coated with cooking spray; cover and chill until firm. Keep remaining mixture at room temperature.
Combine lemon-flavored gelatin and boiling water in a small bowl, stirring 2 minutes or until gelatin dissolves; set aside.
Place cheese in a medium bowl; beat at medium speed of an electric mixer until smooth. Gradually add skim milk, beating well. Add lemon-flavored gelatin mixture, and beat well. Let cool to room temperature. Pour over congealed apple-gelatin mixture. Cover and chill just until firm.
Spoon remaining apple-gelatin mixture over cheese mixture. Cover and chill until firm. To serve, cut into rectangles.