Setting duration AND start position for a MediaElement

I want to play an MP3 file for a certain duration, starting at a certain position, in a WPF app. I want to do this in the code-behind (C#) not the XAML.
In my handler for the "Play" button, I can set the duration easily like this (5000 ms just for example)

            myTimeLine.Source = _MyMediaElement.Source;
            myTimeLine.Duration = (TimeSpan.FromMilliseconds(5000));
            MediaClock mc = myTimeLine.CreateClock();
            _MyMediaElement.Clock = mc;
            _MyMediaElement.Play()

Or I can set the starting position easily like this . . .

            _MyMediaElement.Position = (TimeSpan.FromMilliseconds(5000));
            _MyMediaElement.Play();

But I can"t do both or I'll get a "Can not perform this operation while a clock is assigned to the media player" exception. What's the correct solution to this? Thanks in advance!!