I has been few years, but here it goes.
We had -400s with it but it was few years ago. There is no way of programing waypoints into the ancdu, if the flight plan has not been cross-loaded into the ancdu prior to the failure; the only way then is to insert LAT/LONG into it. If my memory serves, it is done simular to a normal entry into the FMC, however it can only track true. One just puts in the lat and long, for each waypoint in sequence and of we go. Maybe someone with fully loaded brain can clarify further.
Regards