Muting not functioning in 3rd edition

Hi, I am porting an application for Series 60 7.0 to Series 60 3 rd edition.
In that i am using muting code as follows. This just mutes the phone without changing the profile.

   RWsSession sess=CCoeEnv::Static()->WsSession();
      TWsEvent event;
      TInt id=sess.FindWindowGroupIdentifier( 0, _L("*Phone?") );

      event.SetType(EEventKey);
      event.SetTimeNow();
      event.Key()->iCode = EKeyDevice1;
      event.Key()->iModifiers = 0;
      event.Key()->iRepeats = 0;
      event.Key()->iScanCode = EStdKeyNull;
      sess.SendEventToWindowGroup( id, event );

It works for 7.0 but not for 9.1. Does any body know the reason why it is not functining.

Waiting for your reply.

Best Regards Vishal