Changing constant force component values via script?

Hello,

I've applied a "Constant force" component to my FPS controller and wondering how to access and changes some values in a function. I took this code directly from the scripting reference but doesn't seem to work.

I tried: (EDITED)

     #pragma strict
 
 var waterLevel : float;
 private var isUnderwater : boolean;
 private var normalColor : Color;
 private var underwaterColor : Color;
 //var constantForce : ConstantForce;
 
 var myParticles : ParticleSystem;
 private var chMotor : CharacterMotor;
 
 function Start () 
     {
         normalColor = new Color (0.5f, 0.5f, 0.5f, 0.5f);
         underwaterColor = new Color (0.22f, 0.65f, 0.77f, 0.5f);
         chMotor = GetComponent(CharacterMotor);
         myParticles.Stop();
     }
 
 function Update () 
     {
             if ((transform.position.y < waterLevel) != isUnderwater) 
             {
                 isUnderwater = transform.position.y < waterLevel;
                 if (isUnderwater) SetUnderwater ();
                 if (!isUnderwater) SetNormal ();
             }
             if(Camera.main.transform.rotation.x < 10)
             {
                 Debug.Log ("Down");
             }
             
             if(Camera.main.transform.rotation.x >= 10)
             {
                 Debug.Log ("Up");
             }
         }
 
 function SetNormal () 
         {
             RenderSettings.fogColor = normalColor;
             RenderSettings.fogDensity = 0.5f;
         }
      
 function SetUnderwater () 
         {
             RenderSettings.fogColor = underwaterColor;
             RenderSettings.fogDensity = 0.03f;
             //constantForce.relativeForce = Vector3(0, 0, 1);
             chMotor.movement.gravity = 2;
             chMotor.movement.maxFallSpeed = 5;
             chMotor.movement.maxForwardSpeed = 4;
             chMotor.movement.maxSidewaysSpeed = 4;
              myParticles.Play();
         }