Squarespace per page custom navigation links - redirect

Question

So I've spent a day on Google, and trying bits of jquery/javascript to do what I'm looking to do and am officially stuck.
I'm building a site using Squarespace, with the Marquee theme applied. I would like to be able to add a custom link in the primary navigation to send users to an alternative language version of each specific page.
But, I'm struggling. Ive found solutions on here that should work, but I don't think I'm applying it right. Ive tried adding a single link to the navigation and using a script on each page (in the code injection point of the head section) point that link somewhere else.
This would mean I have a single link in the navigation (which is standard across the site) pointing users to whichever page I want...on a per page basis. I know there is a solution out there....just can't make it work!
The section I need the link to work from is:
<div id="desktopNav" data-content-field="navigation-mainNav" data-annotation-alignment="bottom left">
<nav class="main-nav" id="yui_3_17_2_1_1450478013910_660">
<div class="nav-wrapper" id="yui_3_17_2_1_1450478013910_659">
<ul class="cf" id="yui_3_17_2_1_1450478013910_658">
<li class="page-collection">
<span>Menu</span>
</li>
</ul>
</div>
</nav>
</div>
None of this can be edited directly though...
I was thinking something like this could work, but I cant work out how to apply it to my situation...
Change href value for a hyperlink
Any help, gratefully received!

Answer 1

I fixed it...using this:
<script src="//ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script type="text/javascript">
$(document).ready(function(){
$('a[href*="original.site"]').attr('href', 'http://website.com');
});
</script>
It allows me to point a single link in the navigation (which cant be edited directly) to whatever I want it to go to.