DataGridView DefaultCellStyle Format for Time Not working

Hi

The DataGridView shows 10:00:00 but I needs 10:00 AM
If my  time is null in the Database I got 00:00:00. But I need only 00:00
I had applied like this.

dgv.Columns("StartTime").DefaultCellStyle.Format = "h:mm tt"
dgv.Columns("EndTime").DefaultCellStyle.Format = "h:mm tt"
This is not working.
This is for Win Application
I got this from http://social.msdn.microsoft.com/Forums/en-US/winformsdatacontrols/thread/987460ad-0be4-446a-91f8-3c49e863a4ba


Thanks.

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