ShellExecute(Application.handle, pchar('OPEN'), pchar(sPostFixName), nil, nil, SW_SHOWNORMAL);

function IsFileUsed(FileName: TFileName): Boolean;
var
  HFileRes: HFILE;
begin
  Result := False;
  if not FileExists(FileName) then Exit;
  HFileRes := CreateFile(PChar(FileName),
    GENERIC_READ or GENERIC_WRITE,
    0,
    nil,
    OPEN_EXISTING,
    FILE_ATTRIBUTE_NORMAL,
    0);
  Result := (HFileRes = INVALID_HANDLE_VALUE);
  if not Result then
    CloseHandle(HFileRes);
end;