  The decay $B^- \to K^- K^- \pi^+$ has been sugested as a test for minimal
supersymmetric standard model and for supersymmetric models with R-parity
violating couplings, in view of its extreme smallnesss in the standard model.
We calculate two long distance contributions to this decay, that associated
with $DD$ and $D\pi$ intermediate states and that induced by virtual $D$, $\pi$
mesons. The branching ratio due to these contributions is $6 \times 10^{-12}$,
which is somewhat smaller than the standard model short distance result,
leaving this decay free for the search of new physics.
