一个菜问题！createoleobject()需要什么控件？(50分)

procedure TForm1.BitBtn2Click(Sender: TObject);
var ExcelApp: Variant;
begin
ExcelApp:= CreateOleObject( 'Excel.Application' );
ExcelApp.WorkBooks.Open( 'C:/My Documents/wnczp/demo.xls' );
ExcelApp.Visible := True;
ExcelApp.WorkSheets[1].Activate;
end;