We report results of a time resolved X-ray Absorption Spectroscopy (XAS) experiment on the oxidation process of epitaxial Y-1(Nd0.05Ba1.95)Cu3Ox superconducting thin films. For the first time Cu K-edge XAS technique has been used to explore local structural changes around the Cu ions during the oxidation process of a high critical temperature superconducting film. The results show that during the oxygenation of a tetragonal Y-1(Nd0.05Ba1.95)Cu3Ox additional local transitions appear in the orthorhombic I phase, which are not linked to long range order transformations as shown by in situ X-ray diffraction experiment. New questions concerning the dynamic microscopic process leading to the oxygenation and eventually to superconductivity of the complex R1+xBa2-xCu3Ox (R = Y or rare earth) compounds arose from these results.