Cut chicken in strips. In skillet bring chicken and stock to simmer over medium high heat. Add celery, onion and sweet peppers. Cook, string often, for about 5 minutes or until chicken is no longer pink and vegetables are tender crisp.
Mix together juice, vinegar, brown sugar, cornstarch and soy sauce until blended. Stir into skillet and bring to a boil. Cook stirring for about 2 minutes until glossy and thickened.
Add oranges and simmer for about 2 minutes or until heated through.