Windows phone 7 如何在wp7代理中更新警报启动日期？

我想在ScheduledAgent中更新报警开始时间，是否可以在wp7中这样做

    protected override void OnInvoke(ScheduledTask task)
    {
        var schedule = Find("AlarmName")

        if (schedule != null)
        {
            var alarm = schedule as Alarm;
            ReplaceAlarm(alarm);
        }

        NotifyComplete();
    }

    private void ReplaceAlarm(Alarm alarm)
    {
        alarm.BeginTime = NewDateTime;
        alarm.ExpirationTime = NewExpirationTime;
        alarm.Content = "new Text";

        try
        {
            ScheduledActionService.Replace(alarm as ScheduledAction);
        }
        catch
        {
        }
    }

提前感谢。

这是不可能的，因为BackgroundAgent不支持ScheduledActionService.Replace方法