change filename into link

I want to change the filename of a link into Indesign. For example: the existing filename is table_EX.jpg and now I want it to change into table_CZ.jpg

I wrote a script, but it seems that it only change ONE link. Who can help me?

#target indesign

// Relink file fileName.js

if (app.documents.length == 0) {

     err("No open document. Please open a document and try again.", true);

}

var myDoc = app.activeDocument;

var myLinks = myDoc.links;

var myCounter = 0;

if (myLinks.length == 0) {

     err("This document doesn't contain any links.", true);

}

for (i = myLinks.length-1; i >= 0 ; i--) {

     var myLink = myLinks;

     var myOldfileName = myLink.name;

     var myNewfileName = myOldfileName.replace("_EX", "_CZ");

     var myNewFile = new File(myNewfileName);

     if (myNewFile.exists) {

          myLink.relink(myNewFile);

          myCounter++;

     }

}    

document.save()

document.close()