In this paper, we improve the performance of Cooperative Balanced Space-Time Block Codes (CBSTBC) by means of a novel relay selection method. The proposed method prevents an error floor with minimal sacrifice from the full diversity for any number of mobile relays. In the new method, the relays transmit their source-relay channel partial information to the destination with one bit and the destination informs the source and the relays about the selected balanced code and the elected relays with few bits of feedback. For a comparison, we consider distributed space time block codes (DSTBC). As expected, DSTBC perform poorly when source-relay channels have low SNR, thus, an error floor is reached. Detailed computer simulations show that, in our proposed method the occurring of the error floor shifts considerably to higher SNR region.