  We calculate the nuclear suppression for $J/\Psi$ and $\Psi'$ production
within a coupled channel approach in the subspace of the $J/\Psi$ and $\Psi'$
states. We are able to explain, why (i) the $J/\Psi$ and $\Psi'$ show the same
suppression from $200\ GeV$ to $800\ GeV$ in proton-nucleus collisions and why
(ii) the $\Psi'$ is absorbed more strongly than the $J/\Psi$ in nucleus-nucleus
collisions at $200\ GeV$. The numerical result which includes only interactions
with nucleons acconts for half of the observed suppression in sulphur-uranium
collisions.
