Run Script from DialogButtonMenu.xml

Hi,
I run a Raspberry PI 2 with a RemotePi from msldigital. So everything works fine but the shutdown via UI won’t work.
I created a shutdown.sh script which is working when i run it manually.
So i tried to link it with the DialogButtonMenu.xml of the confluence skin which i’m using.
i Substituted the comand:
“<“onclick>Powerdown()”<”/onclick>
with
“<“onclick>System.Exec(”/etc/shutdown.sh”)"<"/onclick>
as described here http://lowpowerlab.com/atxraspi_r1/
but when i use the Powerdown button on the UI nothing happens
may someonecan help me.

greez schinni