Is it possible to modify this script to include subfolders?

I have tried to do this with no luck. This script works great, but how to I make it apply to all sub-folders? Thanks for any suggestions.

#target bridge  

if( BridgeTalk.appName == "bridge" ) { 

descToTitle = MenuElement.create("command", "Keys to Title", "at the end of Tools");

}

descToTitle.onSelect = function () {

if (ExternalObject.AdobeXMPScript == undefined) ExternalObject.AdobeXMPScript = new ExternalObject("lib:AdobeXMPScript");

var thumb = app.document.selections;

    for(var s in thumb){

if(thumb.hasMetadata){

        var selectedFile = thumb.spec;

  var myXmpFile = new XMPFile( selectedFile.fsName, XMPConst.UNKNOWN, XMPConst.OPEN_FOR_UPDATE);

  var myXmp = myXmpFile.getXMP();

         var Description =  getArrayItems(XMPConst.NS_DC, "keywords");

        myXmp.deleteProperty(XMPConst.NS_DC, "title");

        myXmp.appendArrayItem(XMPConst.NS_DC, "title", Description, 0, XMPConst.ALIAS_TO_ALT_TEXT);

        myXmp.setQualifier(XMPConst.NS_DC, "title[1]", "http://www.w3.org/XML/1998/namespace", "lang", "x-default");

    }

function getArrayItems(ns, prop){

var arrItem=[];

try{

var items = myXmp.countArrayItems(ns, prop);

for(var i = 1;i <= items;i++){

arrItem.push(myXmp.getArrayItem(ns, prop, i));

     }

return arrItem;

}catch(e){alert(e +" Line: "+ e.line);}

}

        if (myXmpFile.canPutXMP(myXmp)) {

        myXmpFile.putXMP(myXmp);

        myXmpFile.closeFile(XMPConst.CLOSE_UPDATE_SAFELY);

         } else {

  xmpFile.closeFile();

        }

    }

}