We have to ensure that this goal will be the first one executed when solving the problem. We simply write

    IloGoal goal = SetTrace(env, traceLevel) &&
                   IloSetTimesForward(env, makespan);

and then pass this goal as an argument to the method solve(IloGoal) of the class IloSolver.

Depending on the value of traceLevel, all the modifications that we are interested in will be printed during the search.