Preheat oven to 350. Prepare a jelly roll pan with cooking spray; set aside. To prepare crust, combine graham cracker crumbs, margarine, and three tablespoons sugar. Pat crumb mixture evenly on bottom of prepared pan. Bake for ten minutes; cool. In a saucepan, combine gelatin and milk. Let stand two minutes. Then, heat over medium heat, stirring constantly, until gelatin is dissolved. Cool to room temperature; set aside. In a mixing bowl, combine all the cream cheese, lemon juice, lemon peel, vanilla extract, and remaining sugar. Add milk mixture. Pour entire mixture over baked crust. Refrigerate until set, four hours.

To serve, decorate to look like a flag, using the blueberries for the stars, and the raspberries for the stripes.