C# process running WMPlayer

Hi all,
I am starting a process using a C# Process object (Process.start). This process object has a ProcessStartInfo memmber with the wmplayer as the executable and the file we need to play as a parameter. So as a say process.start , the WMPlayer starts playing the file as expected.
My objective is to issue a process.CloseMainWindow, once the file has been played. Question is how do I know when the file has completed playing. Is there a property in the process object that can help or do I need to explore some other route?
Thanks a lot for any help
Sudarshan