[Bargest]

Код:

OverlapRead.hEvent := CreateEvent(nil, true, false, nil);
  if OverlapRead.hEvent = 0 then
  begin
    ShowMessage('Ошибка создания события.');
    exit;
  end;
//и жду данных:
  if not WaitCommEvent(hPort, dwMask, @OverlapRead) then
    begin
      if GetLastError = ERROR_IO_PENDING then
        WaitForSingleObject(OverlapRead.hEvent, INFINITE)
      else
      begin
        ShowMessage('Ошибка при ожидании данных.');
        exit;
      end;
    end;