Va. Code § 20-74
Any order of support or amendment thereof entered under the provisions of this chapter shall remain in full force and effect until annulled by the court of original jurisdiction, or the court to which an appeal may be taken; however, such order of support or terms of probation shall be subject to change or modification by the court from time to time, as circumstances may require, but no such change or modification shall affect or relieve the surety of his or her obligation under such recognizance, provided notice thereof be forthwith given to such surety. No support order may be retroactively modified, but may be modified with respect to any period during which there is a pending petition for modification in any court, but only from the date that notice of such petition has been given to the responding party.
Va. Code § 20-74