Large variations in muon flux above 1 GeV are observed in GRAPES-3 muon telescope during thunderstorm activity as a result of acceleration of muons in the atmospheric electric fields. To interpret this phenomenon quantitatively, detailed Monte Carlo simulations had to be carried out using the CORSIKA package. In CORSIKA the effects of applied electric field can be simulated by the option EFIELD. However, this option works only for electrons, and positrons as a consequence the variation observed in the GRAPES-3 muon flux could not be simulated. To address this issue, we extended the EFIELD option to simulate applied electric field on charged pions, kaons, and muons. This extension also allows the user to define the cloud height where the electric field exists. Initial simulations show that at high electric potentials, the muon flux decreases irrespective of its polarity. Detailed results of the simulations will be presented at the conference.