Effects of dust grain charge fluctuation, obliqueness and external magnetic field on a finite-amplitude dust acoustic solitary potential in a magnetized dusty plasma, consisting of electrons, ions and charge-fluctuating dust grains, are investigated using the reductive perturbation method. It is shown that such a magnetized dusty plasma system may support a dust acoustic solitary potential on a very slow time scale involving the motion of dust grains, whose charge is self- consistently determined by local electron and ion currents. The effects of dust grain charge fluctuation, external magnetic field and obliqueness are found to modify the properties of this dust acoustic solitary potential significantly. The implications of these results for some space and astrophysical dusty plasma systems, especially planetary ring systems and cometary tails, are briefly mentioned.