Preheat oven to 350 degrees F. Foil AND grease (or use non-stick foil) a 13x9 baking pan. Sift flour, baking soda and salt into medium bowl.
Beat butter and brown sugar in large bowl until creamy. Add eggs and vanilla; beat until smooth. Gradually stir in flour mixture Spread half of batter in prepared pan. Bake 8 minues; cool 5 minutes on wire rack.
Meanwhile, melt caramels and evaporated milk in nonstick saucepan over very low heat. Reserving 2 tablespoonfuls for drizzle, GENTLY SPOON remaining caramel mixture over baked layer in pan. Drop tablespoonfuls of remaining batter over caramel layer, swirl slightly with knife.
Bake 25 minutes or until golden brown. Cool completely in pan on wire rack. Cut into squares. Reheat reserved caramel, if necessary; drizzle over bars.