We develop a new algorithm for the production and propagation of cosmic ray (CR) secondary elements within the framework of Cosmic Ray Energy SPectrum (CRESP) module of Piernik MHD code (Ogrodnik et al. ApJS 253, 18, 2021). CRESP is based on the piece-wise power-law (coarse-grained) method for self-consistent and numerically efficient cosmic ray (CR) propagation in the magnetized ISM of galaxies. We demonstrate the capability of our code to model spectral evolution of multiple CR species, including primary ones, as secondary products obtained by spallation process. We perform a series of stratified box test simulation which reproduce the physical conditions of the interstellar medium of galaxies such as the Milky Way. We show preliminary results concerning secondary 11B to primary 12C ratio, suggesting that this observable depends on parameters such as diffusion of CR or density of the gas. Future extension of the present work towards modelling of hadronic gamma-ray emission is also discussed.