When does Virginia trial court lose jurisdiction to modify sentence of defendant who doesn't go to state prison

In Neely v. Com., the Virginia Court of Appeals in a decision by Judge Benton, joined by Judge Humphreys with Senior Judge Coleman dissenting, held that the trial court erred when it concluded it no longer had jurisdiction to modify the sentence of a criminal defendant who apparently was transferred from the local jail not to the custody of the Virginia Department of Corrections but instead to federal prison.