Combine sugar and corn starch in medium saucepan. Drain mandarin oranges, reserving liquid. Reserve mandarin oranges for later use. Add enough water to reserved liquid to measure 3/4 cup. Gradually stir into sugar mixture. Bring to boil on medium heat, stirring constantly; cook and stir 1 min. Add to dry jelly powder in medium bowl; stir 2 min. until completely dissolved. Refrigerate 1 hour or until thickened, stirring occasionally.