PLACE potatoes in large saucepan. Add water to cover. Bring to boil; cook 10 minutes or until fork-tender. Drain and cool slightly.
MIX mayonnaise, Mustard, salt, sugar and pepper in large bowl until well blended. Add potatoes; toss to coat well. Add celery, green onions, and eggs; toss gently.
COVER and refrigerate at least 2 hours or until ready to serve.