Try this example which is similar to what you needed :
DateTime a = new DateTime(2008, 01, 02, 06, 30, 00);
DateTime b = new DateTime(2008, 01, 03, 06, 30, 00);
TimeSpan duration = b - a;
String result = TimeSpan.FromTicks(duration.Ticks * 5).ToString();
Hope this helps!