We have recently reported colossal magnetoresistance (CMR) in NdMnAsO0.95F0.05. The CMR in NdMnAsO1-xFx arises due to competition between a strongly correlated antiferromagnetic insulating phase and a paramagnetic semiconductor with field. In order to further investigate the CMR in NdMnAsO0.95F0.05 we have synthesised samples NdMn1-xCoxAsO0.95F0.05 (x = 0.00, 0.03, 0.06, 0.09, 0.12 and 0.15). Magnetoresistivity results show that the low temperature CMR is quickly reduced with increasing Co doping. Susceptibility and resistivity measurements suggest a ferromagnetic transition occurs at Tc = 22 K, 130 K and 155 K for x = 0.09, 0.12 and 0.15 respectively. NdMnAsO0.95F0.05 is antiferromagnetic with a transition temperature TMn = 356 K. In this experiment we plan to investigate the magnetic phase diagram of electron doped NdMn1-xCoxAsO0.95F0.05 (x = 0.03, 0.06, 0.09, 0.12 and 0.15).