For the bars, preheat oven to 350 degrees Fahrenheit and follow the directions on the package for making the filling and crust. Bake crust according to package directions. While it's baking, prepare the crumb topping by pressing and mixing all ingredients together with your hands until it forms coarse crumbs. Pour the lemon filling over the hot crust, sprinkle evenly with blueberries, then sprinkle on the crumb topping. Bake for approximately 26-30 minutes, or just until the edges begin to brown. Remove from oven, allow to cool to room temperature, then chill for 2 hours in the refrigerator to make slicing easier. Make the glaze by whisking together powdered sugar and lemon juice. Drizzle over bars. Slice and serve. Store in the refrigerator.