Find closest target on NavMesh for many possible targets

Hello, I'm trying to find the closest target, but no by absolute distance, but by distance of path on my NavMesh, my actual script is this :

 //nma is NavMeshAgent;

     Resource[] ress=FindObjectsOfType(typeof (Resource))as Resource[];
                 foreach(Resource res in ress)
                 {
                     nma.SetDestination(res.transform.position);
                     nma.Stop();
                     while(nma.pathPending)
                     {
                         yield return null;
                     }
                     float currentDistance=Tools.PathLength(nma.path);
                     if(currentDistance<currentNearestResourceDistance)
                     {
                         currentNearestResourceDistance=currentDistance;
                         nearestResourceTrans=res.transform;
                         resourceFound=true;
                     }
                 }
             

But my script calculates and checks a path for ALL targets before to pick the best target, how could i check around my source and stop when i found the first target on the navmesh tree?