Heat oven to 350 degrees F. Grease 13" x 9" pan. In large bowl, combine cake mix, butter and 2/3 cup of the milk. Mix well. Spread half of batter (about 2 cups) in greased pan. Bake at 350 degrees for 15 minutes.
Meanwhile, in small saucepan, heat caramels with remaining 1/3 cup milk over low heat until melted, stirring constantly.
Remove pan from oven, sprinkle with 1 cup of the candy-coated baking bits. Drizzle with caramel mixture. Drop remaining batter by heaping teaspoonfuls over caramel mixture. Sprinkle with remaining 2/3 cup of candy-coated baking bits.
Return to oven, bake at 350 degrees F for an additional 20-24 minutes or until center is set. Cool 1 hour or until completely cooled. Cut into bars.