Travel to and from Murren, Bernese Oberland

Trying to find if it's possible to get down from Murren to Lauterbrunnen after 8 pm (other than by walking). The railway via Grutshalp and cable car seems to stop at 8 pm and the Murren Stechleberg cable car at the same time. We have friends in Wengen who can get back up from Lauterbrunnen to Wengen much later than this, but cannot seem to get down from Murren. I have spent nearly an afternoon looking through timetables. Any help appreciated. August 4 - 15 2012. Thanks