The evolution of the crystal structures and magnetic ordering of layered cobalt oxide chalcogenides will be probed as a function of composition. The systems Sr2CoO2Cu2-zSe2 and Sr2CoO2Ag2-zSe2 are obtained by the removal of some of the copper or silver from the parent materials (with z = 0) using an iodine solution. This process is topotactic and conserves the basic structure. The parent materials show long range antiferromagnetic ordering of the Co sublattice with large orbital enhancements to the moments and evidence for competing magnetic structures. Variable temperature high resolution neutron diffraction will probe of the effect of the chemical oxidation on the long range magnetic order and the competition between magnetic ground states and this will give insight into the fundamental magnetic, electronic and transport properties of these materials.