  The extraction of hadron-hadron scattering parameters from lattice data by
using the L\"uscher approach becomes increasingly complicated in the presence
of inelastic channels. We propose a method for the direct extraction of the
complex hadron-hadron optical potential on the lattice, which does not require
the use of the multi-channel L\"uscher formalism. Moreover, this method is
applicable without modifications if some inelastic channels contain three or
more particles.
