[lmikle]

Ну, у тебя почти получилось:

Код:

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    gbCheckboxes: TGroupBox;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
    ACB : Array [1..20,1..10] Of TCheckBox;
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
  I, J : Integer;
begin
  For J := 1 To 10 Do
    For I := 1 To 20 Do
      Begin
        ACB[I,J] := TCheckBox.Create(Self);
        ACB[I,J].Width := ACB[I,J].Height + Self.Canvas.TextWidth('888');
        ACB[I,J].Top := 16 + (J-1)*(ACB[I,J].Height+8);
        ACB[I,J].Left := 8 + (I-1)*(ACB[I,J].Width+8);
        ACB[I,J].Caption := IntToStr((J-1)*20 + I);
        ACB[I,J].Parent := gbCheckboxes;
      End;
end;

end.

PS. Мне по кнопке удобнее отлаживать.