In a medium saucepan, mix 3/4 cup of the raspberries with the jelly and bring to a boil over medium-high heat. Reduce the heat to medium. In a medium bowl, combine the remaining raspberries with the cornstarch, and then add to the saucepan; cook, stirring constantly, until thickened. Remove the pan from the heat and stir in the butter. Cool berry mixture, and then stir in the orange juice, and refrigerate until chilled. Serve over vanilla ice cream.