ASP.NET GridView second header row to span main header row

I took the accepted answer approach, but added the header to the existing GridView instead of a custom inherited GridView.

After I bind my GridView, I do the following:

/*Create header row above generated header row*/

//create row    
GridViewRow row = new GridViewRow(0, -1, DataControlRowType.Header, DataControlRowState.Normal);

//spanned cell that will span the columns I don't want to give the additional header 
TableCell left = new TableHeaderCell();
left.ColumnSpan = 6;
row.Cells.Add(left);

//spanned cell that will span the columns i want to give the additional header
TableCell totals = new TableHeaderCell();
totals.ColumnSpan = myGridView.Columns.Count - 3;
totals.Text = "Additional Header";
row.Cells.Add(totals);

//Add the new row to the gridview as the master header row
//A table is the only Control (index[0]) in a GridView
((Table)myGridView.Controls[0]).Rows.AddAt(0, row);

/*fin*/