Ошибки при экспорте из StringGrid в Excel

function TForm1.GetExcelFileName: String;
begin
  Result := ExtractFilePath(Application.ExeName) + Edit6.Text;
 
  if LowerCase(ExtractFileExt(Result)) <> EXCEL_FILE_EXT then
    Result := Result + EXCEL_FILE_EXT;
end;
 
procedure TForm1.Button2Click(Sender: TObject);
var
 ExcelApp, Sheet: variant;
 Col, Row: Word;
begin
  //*******************
ExcelApp := CreateOleObject('Excel.Application');
  try
    ExcelApp.Visible := false;
 
    ExcelApp.Workbooks.Add;
    Sheet := ExcelApp.ActiveWorkbook.Worksheets[1];
 
    for Col := 0 to StringGrid1.ColCount - 1 do
      for Row := 0 to StringGrid1.RowCount - 1 do
        Sheet.Cells[Row + 1, Col + 1] := StringGrid1.Cells[Col, Row];
 
    ExcelApp.ActiveWorkbook.SaveAs(GetExcelFileName);
 
    ShowMessage('Ok!');
  finally
    ExcelApp.Application.Quit;
    ExcelApp := unassigned;
    Sheet := Unassigned;
  end;
//*******************
end;

const
  EXCEL_FILE_EXT = '.xls';

Sheet.Cells[Row + 1, Col + 1] := '''' + StringGrid1.Cells[Col, Row];

ExcelApp.DisplayAlerts :=False;

EXCEL_FILE_EXT = '.xlsx'; //для новых версий

Sheet.Cells[Row + 1, Col + 1] := '''' + StringGrid1.Cells[Col, Row];

procedure TForm1.Button1Click(Sender: TObject);
var
  E: OleVariant;
  Range: OleVariant;
begin
  E:= CreateOleObject('Excel.Application');
  E.WorkBooks.Add;
  Range:= E.ActiveWorkbook.Worksheets[1].Range['A1'];
  Range.Value:= 'Hello';
  Range.Font.Bold:= True;
  Range.Font.Color:= clRed;
  E.Visible:= true;
end;