You can use the German rail site to research the train schedules: http://bahn.hafas.de/bin/query.exe/en

You will most likely select a train that goes from Paris-Lyon station and you should find out if your destination in Interlaken is closer to Interlaken West or Interlaken Ost (most likely) so you don't get off at the wrong station.

Note that the route will involve changing trains and that reservations are mandatory on the TGV.

You can use this form on the SNCF site to ask about luggage storage at Paris-Lyon: http://www.voyages-sncf.com/dynamic/faq.mail?_LANG=UK&type_mail=2

Hope that helps, Linda