I used the approach recommended by Brij and achieved the result. the code is following:
TimeSpan myTimeSpan1 = new TimeSpan(DateTime.Now.Hour, DateTime.Now.Minute, DateTime.Now.Second);
TimeSpan myTimeSpan2 = new TimeSpan(20, 00, 00);
TimeSpan TsObj = new TimeSpan();
TsObj = myTimeSpan2.Subtract(myTimeSpan1);
Int32 milsec = Convert.ToInt32(TsObj.TotalMilliseconds);
My_Timer = new System.Threading.Timer(timer_click, null, milsec, 0);
Thanx for posting.