How to merge two column headers of a datagridview

Private Sub dataGridView1_Paint(ByVal sender As Object, ByVal e As PaintEventArgs) Handles DataGridView1.Paint
      Try
          Dim colList ="Mon,tues,wed"
          Dim clst As String() = colList.ToString.Split(",")
          Dim j As Integer = 0
 
          While j < DataGridView1.ColumnCount - 1 '10
              Dim r1 As Rectangle = Me.DataGridView1.GetCellDisplayRectangle(j, -1, True) 'see -1 that is row=-1 means header cell
              Dim w2 As Integer = Me.DataGridView1.GetCellDisplayRectangle(j + 1, -1, True).Width
              r1.X += 0
              r1.Y += 0
              '            r1.Width = r1.Width + w2 -2
              r1.Width = ((DataGridView1.ColumnCount / clst.Count) * w2)
              r1.Height = r1.Height / 2
 
              e.Graphics.FillRectangle(New SolidBrush(Me.DataGridView1.ColumnHeadersDefaultCellStyle.BackColor), r1)
              Dim format As New StringFormat()
              format.Alignment = StringAlignment.Center
              format.LineAlignment = StringAlignment.Center
 
              e.Graphics.DrawString(clst(j / ((DataGridView1.ColumnCount / (clst.Count + 1)) + 1)), Me.DataGridView1.ColumnHeadersDefaultCellStyle.Font, New SolidBrush(Me.DataGridView1.ColumnHeadersDefaultCellStyle.ForeColor), r1, format)
              j += (DataGridView1.ColumnCount / clst.Count)
          End While
      Catch ex As Exception
      End Try
    End Sub