Hi,
If you are using EP 7.3x , you can use the LSAPI javascript methods to get the current launched navigation node.
see the following (and other links in same area):
http://help.sap.com/saphelp_nw73/helpdata/en/31/7ded15d1164c3f9847f886f4a89b3c/content.htm
Best Regards,
Tal