a.cs

private const int   TCM_FIRST       = 0x1300;
private const int   TCM_SETPADDING  = TCM_FIRST + 43;

private const int   PADDING_X   = 24;
private const int   PADDING_Y   = 2;

protected override void WndProc( ref Message m )
{
  if( m.Msg == TCM_SETPADDING )
  {
    // The vertical padding is the high-order word and the horizontal the low-order word of the lParam
    m.LParam = new IntPtr( ( PADDING_Y << 16 ) | ( PADDING_X & 0xFFFF ) );
  }

  base.WndProc( ref m );
}