Thinly slice pork diagonally across the grain. Combine juice, mustard, sugar and cornstarch; set aside. Cook mushrooms and onions in oil in large skillet over medium-high heat. Remove from skillet. Add pork and cook until browned. Stir in mushroom mixture, rice and reserved juice mixture. Cook, stirring frequently, until thoroughly heated. Add oranges, and toss lightly until heated. Transfer to serving dish and sprinkle with almonds.