C / C++ / MFC

class CMyUIThread: public CWinThread
{
  public:
    CMyUIThread()
    {
      // some synchronization code could be needed here
      activeThreads.insert(this);
    }
    ~CMyUIThread()
    {
      // some synchronization code could be needed here
      activeThreads.erase(this);
    }
  protected:
    static void BroadCastMessage(UINT Msg,WPARAM wParam,LPARAM lParam)
    {
      for(activeThreadsIterator it=activeThreads.begin();it!=activeThreads.end();++it){
        it->PostThreadMessage(Msg,wParam,lParam);
      }
    }
  private:
    static std::set<CMyUIThread*> activeThreads;
    typedef std::set<CMyUIThread*>::iterator activeThreadsIterator;
};