When I append an additional variable to a string it stops working

I have a function which creates a new tif file in a folder on the desktop. It has a global variable 'bCode' that works but as soon as I append an additional variable 'cCode' it no longer works. Any idea what would cause this?

This works

var bCode = "007745";
function save4x6() {
    var saveFileTif = new File("~/Desktop/" + bCode + "_Mock_ups/" + bCode + "_CVR.tif"); 

this doesn't, just adding the additional variable cCode it fails, it doesn't output. 

var bCode = "007745";
var cCode = "NLA";
function save4x6() {
    var saveFileTif = new File("~/Desktop/" + bCode + "_Mock_ups/" + bCode + "_CVR" + cCode+".tif");