Melt caramels with milk and margarine. Pour this over cookies in pan.
Cream together cream cheese, powdered sugar, and 1 cup Cool Whip. Spread over caramel mixture.
Top with remaining Cool Whip.
Sprinkle with 12 finely crushed Oreos. Sprinkle with pecans and/or Heath bits, if desired.
Refrigerate for about 2 hours.