I's not working because onNavMeshUpdate string comparation will never succeed.

DefineEngineMethod(NavPath, onNavMeshUpdate, void, (const char *data),,
   "@brief Callback when this path's NavMesh is loaded or rebuilt.")
{
   if(object->mMesh && !dStrcmp(data, object->mMesh->getIdString()))
      object->plan();
}

Engine/source/navigation/navMesh.cpp

@@ -838,7 +838,7 @@ void NavMesh::buildNextTile()
          ctx->stopTimer(RC_TIMER_TOTAL);
          if(getEventManager())
          {
-            String str = String::ToString("%d %.3f", getId(), ctx->getAccumulatedTime(RC_TIMER_TOTAL) / 1000.0f);
+            String str = String::ToString("%d", getId());
             getEventManager()->postEvent("NavMeshUpdate", str.c_str());
             setMaskBits(LoadFlag);
          }