Coronal Mass Ejections (CMEs) are responsible for some of the most severe space weather at Earth. Major geomagnetic storms arise when CMEs carry large amounts of magnetic flux as they propagate in the solar wind. If these magnetic fields have a southward orientation (oppositely directed to the magnetic field at the Earth's magnetopause), they can cause a geomagnetic storm. Predicting in advance whether observed CMEs will carry geoeffective magnetic fields is a long-term priority for the CCMC at NASA GFSC and other groups within NASA as well. We propose to combine the existing CORHEL (Corona-Heliosphere) model of the solar corona and solar wind with a robust technique for generating simulated CMEs. When successfully completed, the new tool, CORHEL-CG, will allow routine simulation of CMEs and represent a leap forward in physics-based space weather prediction models.