  We study the effect of an external magnetic field on the transport properties
of a quantum dot using a recently developed extension of the functional
renormalization group approach to non-equilibrium situations. We discuss in
particular the interplay and competition of the different energy scales of the
dot and the magnetic field on the stationary non-equilibrium current and
conductance. As rather interesting behavior we find a switching behavior of the
magnetic field for intermediate correlations and bias voltage.
