We have developed a robust but user-friendly computer program for the synthesis and inversion of Stokes profiles caused by the joint action of the Hanle and Zeeman effects in some spectral lines of diagnostic interest. The influence of radiative transfer on the emergent spectral line radiation is taken into account through a suitable slab model. The dynamical and magnetic properties of the observed plasma structure are inferred from the observed Stokes profiles via an efficient inversion algorithm based on global optimization methods. Here we introduce it briefly to the solar and stellar physics community by showing the first results of an application to the He I 10830 Å multiplet, whose aim is to obtain empirical information on the strength and orientation of the magnetic field vector in an internetwork region of the solar chromosphere.