Heat oven to 170°C. Grease or spray bottom only of 13x23cm pan.
In large bowl, beat dry cake mix and butter with electric mixer on low speed until crumbly; reserve 180 grams. Press remaining crumbly mixture in bottom of pan.
In same bowl, beat cream cheese, yogurt and frosting on medium speed until smooth. Beat in eggs until blended. Pour over mixture in pan. Sprinkle with reserved crumbly mixture.
Bake 40 to 45 minutes or until center is set. Cool 30 minutes. Refrigerate at least 2 hours until chilled. Just before serving, stir strawberries and blueberries into pie filling. Top each serving with berry mixture. Store covered in refrigerator.