trying to access to a variable (m_GravityMultiplier) of the FirstPersonController script from a Child of the FPSController

I have a Cube that it's child of FPSController and depending of a change in the rotation of this cube i want to manipulate the "GravityMultiplier" from the FirstPersonController Script. How can I make a reference to it and change it during run time?

This is my code so far...

using UnityEngine; using System.Collections; using UnityStandardAssets.Characters.FirstPerson;

public class paracaidas : MonoBehaviour {

 public GameObject FPS;
 public GameObject Cubo;

 void Start () {

     FPS = GameObject.Find ("FPSController").GetComponent<FirstPersonController> ();
 
 }
 
 // Update is called once per frame
 void Update () {

     if (Cubo.transform.eulerAngles.x >= 70) {
         
     }
 
 }

}