Сложная шапка datagridview

someDataGridView.RowHeadersVisible = false;

using System;
using System.Drawing;
using System.Windows.Forms;
 
public class Form1 : System.Windows.Forms.Form
{
 
    private DataGridView someDataGridView = new DataGridView();
 
    public Form1()
    {
        this.Load += new EventHandler(Form1_Load);
    }
 
    private void Form1_Load(System.Object sender, System.EventArgs e)
    {
        this.Size = new Size(1400, 250);
        SetupDataGridView();
        PopulateDataGridView();
    }
 
    private void SetupDataGridView()
    {
        this.Controls.Add(someDataGridView);
        someDataGridView.RowHeadersVisible = false;
        someDataGridView.Dock = DockStyle.Fill;
 
        someDataGridView.Columns.Add("0", "00");
        someDataGridView.Columns.Add("1-01", "01");
        someDataGridView.Columns.Add("1-02", "02");
        someDataGridView.Columns.Add("1-03", "03");
        someDataGridView.Columns.Add("1-04", "04");
        someDataGridView.Columns.Add("2-01", "01");
        someDataGridView.Columns.Add("2-02", "02");
        someDataGridView.Columns.Add("2-03", "03");
        someDataGridView.Columns.Add("2-04", "04");
        someDataGridView.Columns.Add("3-01", "01");
        someDataGridView.Columns.Add("3-02", "02");
        someDataGridView.Columns.Add("3-03", "03");
        someDataGridView.Columns.Add("3-04", "04");
 
        someDataGridView.ColumnHeadersHeight = someDataGridView.ColumnHeadersHeight * 2;
        someDataGridView.Columns[0].HeaderCell.Style.Alignment = DataGridViewContentAlignment.MiddleCenter;
        someDataGridView.ColumnHeadersDefaultCellStyle.Alignment = DataGridViewContentAlignment.BottomCenter;
        someDataGridView.CellPainting += new DataGridViewCellPaintingEventHandler(someDataGridView_CellPainting);
        someDataGridView.Paint += new PaintEventHandler(someDataGridView_Paint);
    }
 
    void someDataGridView_Paint(object sender, PaintEventArgs e)
    {
        string[] titles = { "1", "2", "3" };
        for (int j = 1; j < 13; )
        {
            Rectangle r1 = someDataGridView.GetCellDisplayRectangle(j, -1, true); //get the column header cell
            r1.X += 1;
            r1.Y += 1;
            r1.Width = r1.Width * 4 - 2;
            r1.Height = r1.Height / 2 - 2;
            e.Graphics.FillRectangle(new SolidBrush(someDataGridView.ColumnHeadersDefaultCellStyle.BackColor), r1);
            StringFormat format = new StringFormat();
            format.Alignment = StringAlignment.Center;
            format.LineAlignment = StringAlignment.Center;
            e.Graphics.DrawString(titles[j / 4],
            someDataGridView.ColumnHeadersDefaultCellStyle.Font, 
            new SolidBrush(someDataGridView.ColumnHeadersDefaultCellStyle.ForeColor), r1, format);
            j += 4;
        }
    }
 
    void someDataGridView_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
    {
        if (e.RowIndex == -1 && e.ColumnIndex > -1)
        {
            e.PaintBackground(e.CellBounds, false);
            Rectangle r2 = e.CellBounds;
            r2.Y += e.CellBounds.Height / 2;
            r2.Height = e.CellBounds.Height / 2;
            e.PaintContent(r2);
            e.Handled = true;
        }
    }
 
    private void PopulateDataGridView()
    {
        string[] row0 = { " ", "3596.58", "0", "0", "705.48", "0", "0", "0", "0", "3596.58", "0.00", "0.00", "705.48"};
        someDataGridView.Rows.Add(row0);
    }
 
 
    [STAThreadAttribute()]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.Run(new Form1());
    }
}