I need to call a C# function from Javascript...

I need to write and read config from a external file, the problem is... The function that write changes in the file is written (evidently) in C#, but the GUI script that calls the C# function is written in Js... If I call it like a Js function not works...

c# function is here: (Writer.cs)

 using UnityEngine;
 using System.Collections;
 using System;
 using System.IO;
 
 public class Writer : MonoBehaviour {
 
     private FileInfo theSourceFile = null;
     private StreamWriter writer = null;
     private string sPath = System.Environment.GetEnvironmentVariable("HOMEDRIVE") 
     + System.Environment.GetEnvironmentVariable("HOMEPATH");
     
     // Function that saves the settings in the config file...
     public void write (int resWidth, int resHeight, int Quality) {
     
         if (Application.platform != RuntimePlatform.OSXWebPlayer &&
             Application.platform != RuntimePlatform.WindowsWebPlayer){
     
             if (File.Exists(sPath + "/VHconfig.txt")){
                 Debug.Log("Configuration file found in " + sPath + "/VHconfig.txt" + ". Deleting...");
                 File.Delete(sPath + "/VHconfig.txt");               
             }
         
             theSourceFile = new FileInfo (sPath + "/VHconfig.txt");
             writer = theSourceFile.CreateText();
         
             writer.WriteLine(resWidth);
             writer.WriteLine(resHeight);
             writer.WriteLine(Quality);
         
             writer.Close();
         }
     }
 }

Is called from Js here:

 Writer.write(changedResWidth, changedResHeight, changedQuality);

Any way to call it from Js??

Thanks a lot.