You have attempted to export dual values when the solver is in primals only mode. In primals only mode dual values are not computed and, therefore, can't be exported. To enable dual computations in Windows versions of LINGO run the Solver|Options command, click the General Solver Tab, and select the Prices option from the Dual Computations list box. To enable dual computations in command-line versions of LINGO use the command: SET DUALCO 1. To enable dual and range computations in Windows versions of LINGO run the Solver|Options command, click the General Solver Tab, and select the Prices and Ranges option from the Dual Computations list box. To enable dual and range computations in command-line versions of LINGO use the command: SET DUALCO 2.