Crush 18 of the cookies into fine crumbs, and the remaining 6 to 1/4 inch crumbs.
In a small bowl mix fine cookie crumbs with melted butter.
Press cookie crumbs/butter mixture into a greased 9 inch springform pan to form a crust and refrigerate.
In medium bowl fold 1/2 cup raspberries into yogurt and spread evenly over the crust.
Sprinkle remaining cookie crumbs over yogurt mixture.
Carefully spread whipped topping evenly over cookie crumbs.
Freeze 4 to 5 hours or until firm. Remove sides of pan.
Top with blueberries and remaining raspberries. Store in freezer.