Line an 8"x8" baking pan with foil. Leave a 2" overhang on two sides. Spray foil with non-stick cooking spray. Set aside.
Crush cookies in a food processor or place in a sealed plastic bag and pound with a rolling pin until you have fine crumbs.
In a medium bowl, stir cookie crumbs and butter together with a fork until moistened. Pour mixture into prepared pan and press firmly to form a crust. Place in refrigertor.
Pour 2 tablespoons water into a small bowl. Then sprinkle gelatin over water. Let it rest while you make the filling.
In a large bowl, beat the cream cheese with an electric mixer for one minute. With the mixer on low, gradually add the sugar substitute. Turn mixer up to medium and beat until sugar is thoroughly combined. Turn mixer off, scrape the bowl, then mix again for a few seconds. Mix in sour cream and vanilla. Heat gelatin mixture in microwave for 20 seconds, then stir until completely dissolved. Turn the mixer on low and slowly add the gelatin to the cream cheese mixture. Mix until thoroughly combined.
Pour cream cheese mixture into crust. Smooth top with an offset spatula. Cover with plastic wrap and refrigerate for three hours or overnight. Cut into bars and serve with blueberry sauce. Store in refrigerator for up to 3 days.
For the blueberry sauce:
In a heavy saucepan, stir together the sugar substitute and cornstarch. Stir in lemon juice and water. Add blueberries. Bring to a boil over medium high heat, stirring constantly. Let it come to a boil and continue boiling for about 2 minutes or until thickened. Stir in butter. Let it cool, then serve with bars. Store sauce in refrigerator with plastic wrap right on top.