[en] Recent calculations have predicted that a bound state between an eta and a nucleus may occur as an intermediate state in pion double charge exchange (DCX). The existence of such a mesic nucleus would lead to a resonance-like structure in the DCX excitation function at fixed momentum transfer. LAMPF Experiment 1140 searched for an η-nucleus bound state in the DCX reaction ¹⁸O(π⁺, π^-)¹⁸Ne(DIAS). An excitation function for this reaction was measured for energies ranging from 350 to 440 MeV and for momentum transfers of q = 0, 105 and 210 MeV/c. The calculated cross sections agree favorably with previously published data. Theoretical calculations predict that a resonance structure will be evidenced by an enhanced cross section at the eta production threshold for this reaction. The measured excitation function has found some evidence of structure in this region