The dynamic behavior of an inverse ferrofluid consisting of diamagnetic, spherical silica particles suspended in the paramagnetic ionic liquid (EMIm)(2)[Co(NCS)(4)] is investigated by means of x-ray photon correlation spectroscopy in the presence of an external magnetic field. Dipole-dipole interactions between the diamagnetic holes in the paramagnetic continuum of the suspending medium induce a direction-dependence of the diffusive motion of the colloidal particles: due to a magnetic repulsion perpendicular to the direction of an external field the diffusive motion of the colloidal particles is selectively frozen in this direction.