Ah - that's a little off my local patch, so I can't be of direct help. I live in Gryon and get out along the Rhône Valley a lot, as well as the occasional trip to the Gstaad region, but I've never gone that extra mile out to Interlaken.
If you haven't found it already, there's a good guide to the distribution of Swiss fauna, which includes detailed maps of every species of butterfly, at
http://lepus.unine.ch/carto/. Go in via the Public Access, then choose Rhopalocera, then navigate to any species you want.
I look forward to your piccies when you get back! You will have a fantastic time.
Guy