private void updateMark(int index, TimeSpan ts)
{
//test if the new mark already exists, if not remove it and add the new one
if (_displayedCollection.Marks.Contains(ts))
{
System.Media.SystemSounds.Asterisk.Play();
}
else
{
_displayedCollection.Marks.RemoveAt(index);
_displayedCollection.Marks.Add(ts);
_displayedCollection.Marks.Sort();
PopulateMarkListFromMarkCollection(_displayedCollection);
UpdateMarkCollectionInList(_displayedCollection);
}
}