We present an exciton Green's function calculation of binding energies and optical absorption in semimagnetic quantum wells as a function of applied magnetic field in Faraday configuration. We follow the heavy hole exciton binding energy as a function of valence band offset and well-width and as function of external magnetic field. Besides that we obtain the spectrally integrated absorption, which is proportional to the oscillator strength and compare it as a function of magnetic field with published experimental results and variational calculations. We predict values of critical fields as function of exchange interaction strengths, which can be fitted with the parameters responsible for the average spin of the magnetic system.