I have run the Bahn.de site for a solution for this route--on 28 June---but am not sure I have the right station for Nancy. I need some help from the rail mavens.

Just looking at the SNCF site, it appears that the principal way to get there is to take a local TER train from Nancy to Basel, from which there are connections to Interlaken.

Not sure what you are asking, Nancy only has one train station which should be called Nancy Ville. The simplest routes only make one stop in Switzerland (at Basel or Bale in French). You have to take a TER and go to Interlaken West.

Thanks---I have found it.

Nancy-Ville is the name of the main train station (and only station TMK) in Nancy - do as Kerouac says - Basel to Berne then change most likely to trains to Interlaken, which has two train station - West and Est (Ost) - Interlaken-Ost is the terminus for mainline trains and the jumping off point for trains up to the Alpine villages like Grindelwald, Wengen, Lauterbrunnen, etc.

Interlaken-West is a mile to the west and in the heart of commercial Interlaken and closer to some hotels than Ost if staying in Interlaken.

Grazie PalenQ, you are correct !