C# DataGridView, Row Headers / Generating

I've been tinkering on a DataGridView class I extended.  I'm trying to make the rows/row headers act something like the Outlook calendar with the timestamps down the side.  9:00 AM, 9:15 AM, etc.

I've been using this code, it makes rows, but only leaves text in the very last row.  In theory I'd like it to do the quarter hours as well for a 24 hour cycle.  I'm pretty sure it's a simple solution but I've gotten too close and it's eluding me.  Thanks in advance for any advice! Again, for some reason this might have assigned the row header, but the only one displayed after it runs is the very last, the rest are blank.

 public void makeTimeStamps()
        {
            this.Columns[0].Name = "Time";

            for (int i = 1; i <= 12; i++)
            {
                string s1 = i.ToString();
                this.Rows.Add();
                this.Rows[i].HeaderCell.Value = i.ToString();
            }
        }

May the fleas of a thousand camels feast happily on the lower regions of your enemies. And may their arms be too short to scratch!