  The coronal magnetic field cannot be directly observed, but in principle it
can be reconstructed from the comparatively well observed photospheric magnetic
field. A popular approach uses a nonlinear force-free model. Non-magnetic
forces at the photosphere are significant meaning the photospheric data are
inconsistent with the force-free model, and this causes problems with the
modeling (De Rosa et al., Astrophys. J. 696, 1780, 2009). In this paper we
present a numerical implementation of the Grad-Rubin method for reconstructing
the coronal magnetic field using a magnetostatic model. This model includes a
pressure force and a non-zero magnetic Lorentz force. We demonstrate our
implementation on a simple analytic test case and obtain the speed and
numerical error scaling as a function of the grid size.
