Setting Timer interval

Question

I have problem with setting timer interval propably because of the type conversion. Please see my code below.
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CODE

TimeSpan HourNow = CurrTime.TimeOfDay;
TimeSpan HourScheduled = new TimeSpan (1,readint,RandomStartMin, 0);
TimeSpan Duration = HourScheduled - HourNow;
timer1.Interval = Convert.ToInt32(Duration.TotalMilliseconds);
timer1.Tick += new EventHandler(DayTicker);
timer1.Start();

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Firs time start is ok, but it is lunching DayTicker() 6 to 10 times in 1 minute, despite interval is set to = 1000000
Please help

When i put there
timer1.Interval = 10000
it works all right