DFM file

object frmMain: TfrmMain
  Left = 0
  Top = 0
  BorderStyle = bsSizeToolWin
  Caption = 'Expand example.'
  ClientHeight = 295
  ClientWidth = 136
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  OnCreate = FormCreate
  PixelsPerInch = 96
  TextHeight = 13
  object grdMain: TcxGrid
    Left = 0
    Top = 0
    Width = 136
    Height = 252
    Align = alClient
    TabOrder = 0
    object tbvMain: TcxGridTableView
      NavigatorButtons.ConfirmDelete = False
      DataController.Summary.DefaultGroupSummaryItems = <>
      DataController.Summary.FooterSummaryItems = <>
      DataController.Summary.SummaryGroups = <>
      object clmYear: TcxGridColumn
        Caption = 'Year'
      end
      object clmPopulation: TcxGridColumn
        Caption = 'Population'
      end
    end
    object lvlMain: TcxGridLevel
      GridView = tbvMain
    end
  end
  object pnlExpand: TPanel
    Left = 0
    Top = 252
    Width = 136
    Height = 43
    Align = alBottom
    TabOrder = 1
    object btnExpand: TButton
      Left = 8
      Top = 6
      Width = 121
      Height = 25
      Caption = 'Expand by year = 1'
      TabOrder = 0
      OnClick = btnExpandClick
    end
  end
end

Expanding example

unit uMain;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, cxGraphics, cxControls, cxLookAndFeels, cxLookAndFeelPainters,
  cxStyles, dxSkinsCore, dxSkinscxPCPainter, cxCustomData, cxFilter, cxData,
  cxDataStorage, cxEdit, cxGridCustomTableView, cxGridTableView,
  cxGridCustomView, cxClasses, cxGridLevel, cxGrid, StdCtrls, ExtCtrls;

type
  TfrmMain = class(TForm)
    grdMain: TcxGrid;
    lvlMain: TcxGridLevel;
    tbvMain: TcxGridTableView;
    clmYear: TcxGridColumn;
    clmPopulation: TcxGridColumn;
    pnlExpand: TPanel;
    btnExpand: TButton;
    procedure FormCreate(Sender: TObject);
    procedure btnExpandClick(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  frmMain: TfrmMain;


implementation

{$R *.dfm}

procedure TfrmMain.btnExpandClick(Sender: TObject);
const
  CurrentYear = 1;
var
  i: Integer;
begin
  for i := 0 to tbvMain.ViewData.RowCount - 1 do
  begin
    if not tbvMain.ViewData.Rows[i].IsData then
    begin
      if tbvMain.ViewData.Rows[i].Values[clmYear.Index] = CurrentYear then
        tbvMain.ViewData.Rows[i].Expand(False);
    end;
  end;
end;

procedure TfrmMain.FormCreate(Sender: TObject);
var
  i: Integer;
begin
  // Prepare some random data.
  Randomize;
  tbvMain.DataController.RecordCount := 10;
  for i := 0 to tbvMain.DataController.RecordCount - 1 do
  begin
    tbvMain.DataController.Values[i, clmYear.Index] := Random(3) + 1;
    tbvMain.DataController.Values[i, clmPopulation.Index] := Random(100);
  end;
end;

end.