Preheat oven to 350°.
Coat a 13 x 9-inch baking pan with cooking spray; dust with 1 tablespoon flour.
Place the sugar, margarine, evaporated milk, and egg whites in a large bowl, and beat with a mixer at medium speed for 1 minute. Lightly spoon 2 cups flour into dry measuring cups, and level with a knife. Combine 2 cups flour, salt, and baking soda in a small bowl, stirring well with a whisk. Gradually add the flour mixture to the sugar mixture, and beat with a mixer at low speed just until blended. Stir in the chips and macadamia nuts.
Spoon the batter into prepared pan. Microwave the syrup at high 45 seconds or until warm, and stir. Drizzle the caramel syrup diagonally across batter. Bake at 350° for 30 minutes or until a wooden pick inserted in center comes out clean. Cool.