The Kobayashi-Maskawa model for CP violation recently passed its first precision test -- the measurement of sin2beta from the CP asymmetry in B0 -> J/psi Ks. Probing other CP-violating phases with B decays is much more challenging. Studying decays of the type B+/- -> D K+/- may be the best way to determine the CP-violating phase (gamma) of the b->u transition relative to the dominant b->c transition. I will present results of an analysis of the [K+pi-]K- final state using 120 million B-Bbar events recorded by the Babar detector at SLAC. The implications of this result on the ultimate precision of the gamma determination from B -> DK decays will also be discussed.