When I click on a row header, the row is selected and no cell is active. How can I do this programmatically

This code adds a method to a derived grid that simulates a mouseclick on the rowheader of the row passed into the method.

	public class MyDataGrid : DataGrid
	{
			
		public const int WM_LBUTTONDOWN = 513; // 0x0201 
		public const int WM_LBUTTONUP = 514; // 0x0202 
		
		[System.Runtime.InteropServices.DllImport('user32.dll')]
		static extern bool SendMessage(IntPtr hWnd, Int32 msg, Int32 wParam, Int32 lParam);

		public void ClickRowHeader(int row)
		{
			//get a point to click
			Rectangle rect = this.GetCellBounds(row, 0);
			Int32 lparam = MakeLong(rect.Left - 4, rect.Top + 4);
		
			//click it
			SendMessage( this.Handle, WM_LBUTTONDOWN, 0, lparam);
			SendMessage( this.Handle, WM_LBUTTONUP, 0, lparam);
		}

		static int MakeLong(int LoWord, int HiWord)
		{
			return (HiWord << 16) | (LoWord & 0xffff);
		}
		
	}
.....
.....
	//usage - myDataGrid is of type MyDataGrid.
	private void button2_Click(object sender, System.EventArgs e)
	{
		myDataGrid.ClickRowHeader(2);
	}