Giant magnetoresistance (GMR) is observed up to -49% in RuSr2R1.8-xY0.2CexCu2O10-d ruthenocuprates. The magnetotransport is very sensitive to lattice effects. As , the mean A site (R0.9Y0.2Ce0.9) cation radius decreases the MR phase boundary is shifted to lower hole doping concentration, p so that superconductivity is observed at lower p. Transitions from ¿MR to +MR and then to superconductivity arise as p increases. We propose to perform a variable temperature, ZF musr study on MuSR in longitudinal geometry on three samples RuSr2Gd1.8-xY0.2CexCu2O10-d (x = 1.0, 0.9, 0.7) in the ¿MR, +MR and superconducting phases respectively in order to probe the magnetic order within the CuO2 planes. A TF experiment will also be performed for RuSr2Gd1.8-xY0.2CexCu2O10-d in order to quantify the musr assessment of superconductivity and to determine how the spin dynamics change around Tc = 16 K.