Need to add advanced _udn into Google Analytics Code

We use a sub-domain for our ecommerce store and as a result we need to add a specific line of code to our Google Analytics Code to make sure that we are tracking the right sub-domain.

The code I have currently hard coded into the template is:

PHP Code:

<script src="http://www.google-analytics.com/urchin.js" type="text/javascript">
</script>
<script type="text/javascript">
_uacct="UA-123456-1";
_udn="mp3car.com";
urchinTracker();
</script> 


And when I use vbSEO's built in feature so that I can take advantage of the outbound links features all I can get is this:

PHP Code:

<script src="http://www.google-analytics.com/urchin.js" type="text/javascript">
</script>
<script type="text/javascript">
_uacct="UA-123456-1";
urchinTracker();
</script> 


How can I add that extra

PHP Code:

_udn="mp3car.com"; 


line that I need?

Hello,

here you go: Two Google Analytics urchinTrackers with Google Analytics Funnel for Registrations