A MESA module that incorporates the effects of surface fossil magnetic fields, applicable for massive OB stars. Work associated with the PhD Thesis of Zsolt Keszthelyi, 2019, Queen's University at Kingston, Canada. 1) The first application for non-rotating models presented by: Petit, Keszthelyi, MacInnis, et al. 2017, MNRAS, 466, 1052 https://ui.adsabs.harvard.edu/abs/2017MNRAS.466.1052P/abstract 2) The module is discussed in https://ui.adsabs.harvard.edu/abs/2020arXiv200106239K/abstract Additionally, it may also be helpful for users to be aware of three papers in this topic that used the Geneva code: Georgy, et al. 2017, A&A, 599, 5 https://ui.adsabs.harvard.edu/abs/2017A%26A...599L...5G/abstract Song, et al. 2018, A&A, 609, 3 https://ui.adsabs.harvard.edu/abs/2018A%26A...609A...3S/abstract Keszthelyi, et al. 2019, MNRAS, 485, 5843 - Paper I https://ui.adsabs.harvard.edu/abs/2019MNRAS.485.5843K/abstract Added 05Sep2019: Ph.D. Thesis has been published at https://qspace.library.queensu.ca/handle/1974/26465