In a medium saucepan combine blueberries, sugar, and lemon juice. Cook over medium heat, 10 minutes, stirring occasionally, until berries have released their juices. Strain through a fine-mesh sieve without pushing on the berries; chill.
To serve, moisten the edge of a tall glass and dip it in blueberry sugar. Fill with 2 ounces blueberry syrup, and top with ice and 4 ounces club soda. Garnish with additional blueberries.