Apr 10, 2012 - 2:22 AM
Hello atanwar,
If I were you, I would go to a ticket office at Lauterbrunnen train station, show them your pass and ask because it's short notice. I guess you will travel for free up to Wengen, get a 25% discount to Kleine Scheidegg and Jungfraujoch, if you use your pass (and still it will depend on the kind of pass you have).