  Following a strategy introduced earlier by the authors, we show that it is
possible to extract |V_{ub}| from the cut hadronic mass spectrum of B decays
without large systematic errors which usually arise from having to model the
Fermi motion of the heavy quark. We present a closed form expression for
|V_{ub}|/|V_{ts}| which is accurate up to corrections of order \alpha_s^2,
\alpha_s \rho, (\Lambda/m_b)^2/\rho, where \rho is the experimental cut
(s_c/m_b^2) on the hadronic mass used to veto charmed decays. Modulo duality
violation errors, which are intrinsic to all inclusive predictions, we estimate
the theoretical error in the extraction to be at the 5% level.
