B4J Question Run .exe of a driver installer under Windows

[Run]
Filename: "{app}\DriverSetup\SETUP.EXE"; Flags: postinstall runascurrentuser unchecked; Description: "Install driver"; Check: IsWin64; AfterInstall: SetElevationBit('{app}\DriverSetup\SETUP.EXE')

[Code]
procedure SetElevationBit(Filename: string);
var
  Buffer: string;
  Stream: TStream;
begin
  Filename := ExpandConstant(Filename);
  Log('Setting elevation bit for ' + Filename);

  Stream := TFileStream.Create(FileName, fmOpenReadWrite);
  try
    Stream.Seek(21, soFromBeginning);
    SetLength(Buffer, 1);
    Stream.ReadBuffer(Buffer, 1);
    Buffer[1] := Chr(Ord(Buffer[1]) or $20);
    Stream.Seek(-1, soFromCurrent);
    Stream.WriteBuffer(Buffer, 1);
  finally
    Stream.Free;
  end;