In 2-quart saucepan, heat berries and cherries over medium heat 5 minutes, stirring occasionally; drain. Stir in 1 1/2 cups sugar and the vanilla. Heat 5 minutes longer, stirring constantly; drain. Reduce heat to low. Stir in corn starch mixture; cook 5 minutes longer or until very thick and gooey, stirring constantly, but gently so as not to mash berries. Remove from heat; let cool about 5 minutes.