We have presented a novel approach to enhance the accuracy of SEEKR2 milestoning simulations of bimolecular complexes for predicting receptor-ligand unbinding rates through quantum me- chanical reparameterization of the ligand charges at the binding site. The QMrebind force field reparameterization method may also be useful to simulate the binding-unbinding processes of receptor-ligand complexes using other enhanced sampling methods besides SEEKR2, such as RAMD, GaMD, etc. This method provides a multi-scale approach for force field parameterization through quantum mechanical treatment of the ligand at its binding site, thereby increasing the accuracy of simulations in estimating the unbinding rates of the ligands. To evaluate the effectiveness of our approach, we implemented this method within the SEEKR2 simulation framework to estimate the ligandunbinding rates for seven host-guest complexes and 17 N-Hsp90inhibitor complexes. Our results showed that the QMrebindreparameterized force field within the SEEKR2 framework outperformed the generic force field in estimating the kinetic properties of receptor-ligand unbinding for most of the complexes. This comparison highlights the potential of the improved force field parameters to enhance the simulation accuracy. Integration of the QMrebind method into SEEKR2 is straightforward, and it can also be used as a standalone package for reparameterizing force field parameters for unbiased MD simulations and other enhanced MD simulation methods.