[Zope] Accessing to the ZOPE_HOME

Hi all: How can access to the value of the "ZOPE_HOME" that Control_Panel shows in the Zope Management Interface?. My target is read in execution time a content of one external method, but my zope server can run over windows or linux, and i must refer the folder when the zope are installed, indeed when the external methos are located, for example: "/usr/lib/zope2.7/Extensions" or "C:\Program Files\Zope-2.7.4-0\Extensions" Thank in advance