Link to Administration

Hello,

I modify my WordPress currently a little bit because I want use it as CMS. But there is one little problem. I include the PHP variable for the administration link into my navigation but the html output is currently:
<li><a href="http://www.kerweborsch-rossdorf.de/cms/wp-admin/">Administration</a></li>

But I must change it to:
<li><a href="http://www.kerweborsch-rossdorf.de/cms/wp-admin/"><span>Administration</span></a></li>

How and where can I do that? I searched in a lot of PHP files but I can’t find that code. Hope someone could help me.

greetings,
Synoxis