Yes, I set it. 
This is my batch start.bat
@ECHO OFF
SET MAYA_LOCATION=C:\Program Files\Autodesk\Maya2012
SET MAYA_RENDER_DESC_PATH=C:\vray\demo_2012_22001\maya_root\bin\rendererDesc
SET VRAY_FOR_MAYA2012_MAIN_x64=C:\vray\demo_2012_22001\maya_vray
SET VRAY_FOR_MAYA2012_PLUGINS_x64=C:\vray\demo_2012_22001\maya_vray\vrayplugins
SET MAYA_PLUG_IN_PATH=C:\vray\demo_2012_22001\maya_vray\plug-ins
SET MAYA_SCRIPT_PATH=C:\vray\demo_2012_22001\maya_vray\scripts
SET MAYA_MODULE_PATH=C:\vray\demo_2012_22001\maya_root\modules
SET XBMLANGPATH=C:\vray\demo_2012_22001\maya_vray\icons
SET PATH=C:\vray\demo_2012_22001\maya_root\bin
"C:\Program Files\Autodesk\Maya2012\bin\maya.exe"