Distributed space-time transmit beamforming approaches potentially improve the throughput and robustness of wireless communications links. In this paper, we propose a distributed, space-time, transmit beamformer formulation that performs simultaneous data transmission and channel probing in the presence of interference. The difficulty is that the data signal corrupts the whitened channel estimate and leads to a loss in signal-to-interference and noise ratio. We examine this loss relative to the optimal solution and propose a diagonal loading technique to reduce the loss.