DTM Data Layer Basics

I'm having trouble getting DTM to recognize my Data Layer variable. I don't know much about JS objects, so I think maybe my problem is just in how I define my Data Layer variable.

First in DTM I created a Data Element called Page_Name

[img]Page_Name.gif[/img]

Notice that I set the default value to "Unknown", which may seem redundant, but I couldn't get s.pageName to take a default value without doing that.

Next I created a Page Load Rule that sets Page name to my object: %Page_Name%

Finally, on my actual page I added this javascript:

    <script>
        //data layer
        var Page_Name = "Homepage"
    </script>

But when I save this page and refresh it, I'm still getting "Unknown" in my pageName parameter being sent to Omniture.

Thanks for your help!

Craig