hsr///////////////////////////////////////////////////////////////////
어디서 저도 봤었는데요....
잘생각이 안나네요 좀더 찾아보시면 정리된예제거 있을겁니다.
unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ComObj, ExtCtrls, ShellAPI;

type
  TForm1 = class(TForm)
    Button1: TButton;
    OpenDialog1: TOpenDialog;
    Panel1: TPanel;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
    EXApp : Variant;
    wnd :  HWND;
begin
   OpenDialog1.Execute;
   EXApp:= CreateOleObject('Excel.Application');
   EXApp.WorkBooks.Open(OpenDialog1.FileName);
   wnd := FindWindow( 'TSrcForm', nil );
   Windows.SetParent( wnd, Panel1.Handle );
   SetWindowPos( wnd, 0, 0, 0, Panel1.width, Panel1.height,
                 SWP_NOZORDER or SWP_SHOWWINDOW );
   EXApp.Visible := True;
end;

procedure TForm1.Button2Click(Sender: TObject);
var
    wnd :  HWND;
    fName : string;
begin
   OpenDialog1.Execute;
   ShellExecute(0, 'open', PChar(OpenDialog1.FileName), nil, nil, SW_SHOWNORMAL);
   fName := ExtractFileName(OpenDialog1.FileName) + ' - 메모장';
   sleep(1000);
   Wnd := FindWindow(nil, PChar(fName) );
   Windows.SetParent( wnd, Panel1.Handle );
   SetWindowPos( wnd, 0, 0, 0, Panel1.width, Panel1.height,
                 SWP_NOZORDER or SWP_SHOWWINDOW );
end;

end.