We propose to measure the structure of glassy Ge2Se3 and GeSe9 which lie at either end of the glass forming region in the Ge-Se system. The motivation is provided by the need to understand the structure-function relationship in materials like Ge-Se where the system properties can be controlled by manipulating the composition. The new data will be used to test the validity of ongoing first principles molecular dynamics (FPMD) simulations which are non-trivial because the electronegativities of Ge and Se are comparable, leading to significant challenges for the density functional theory based FPMD calculations. The diffraction data are also required to normalise the results, and to extract the Debye-Waller factor, from our recent inelastic neutron scattering experiments using MARI to measure the vibrational density of states (VDOS).