update usage

CountDown.cs

IEnumerator Waiting(TimeSpan elapsedTimeSpan,
    System.Action<TimeSpan> timeCallback,
    System.Action callback)
{
    for (;elapsedTimeSpan.CompareTo(TimeSpan.Zero) >= 0;)
    {
        if (timeCallback != null) { timeCallback(elapsedTimeSpan); }

        elapsedTimeSpan -= new TimeSpan(0, 0, 1);
        yield return new WaitForSeconds(1.0f);
    }

    if (callback != null)
    {
        callback();
    }
}

//Usage
//
//var cdCoroutine = cd.Waiting( new System.TimeSpan(0, 0, 10),
//    elapsedTime =>
//    {
//        timeValue.text = string.Format( "{0:dd\\.hh\\:mm\\:ss}", elapsedTime );
//    },
//    null );
// 
//StartCoroutine( cdCoroutine );