In a bowl, combine sugar and pectin, and stir until well blended. Place blueberries in a thick-bottomed pot. Stir in sugar-pectin mixture, and add lemon juice. Cook over high heat for 35 minutes, stirring every couple of minutes. Sauce should reach a medium-thick consistency. Note: Sauce can be prepared in advance to be used in the champagne cocktail or blueberry-port reduction.