Combine sugar, cornstarch & salt in a heavy pan. Add just enough water to dissolve cornstarch. Add cranberries. Cook until thickened. Add raspberries and cherry pie filling. Stir gently. Fill 2 pie shells and top with crust. Crimp crust edges and decorate center with slits in crust. Bake 35 min at 425oF.
Substitution suggestions: Try other fruit combinations and adding extracts or spices.
