Redirecting to external URL in web dynpro application accessed in portal

Hi All,

I want to redirect to external url (eg http://www.google.com) on click of button in web dynpro application, but I am accessing the application through portal.

I tried SAP's recommended approach

1) EXIT PLUG :http://help.sap.com/saphelp_nw70ehp1/helpdata/en/83/e7c24122e3c317e10000000a155106/frameset.htm

it works when i test web dynpro application separately but when I run it through Portal it gave me Error: saying use portal navigation when running inside portal and do not fire exit plug to navigate to external URL

2) so i tried

WDPortalNavigation.navigateAbsolute( "http://www.google.com", WDPortalNavigationMode.SHOW_INPLACE,(String) null,(String) null,WDPortalNavigationHistoryMode.NO_DUPLICATIONS,(String) null,(String) null,(String) null);

this wont work as google.com web page is not part of portal content's (Role/iview)

3) I also tried

WDClientUser.forceLogoffClientUser("http://www.google.com");

again this work's when web dynpro application is tested standalone but when I run it through portal it doesn't work 

please let me know if I need to follow some other approach to do this .

Thanks !