Your calendar link is currently in the source you provided. Find the following code:
Code:
<td class="vbmenu_control"><a href="calendar.php$session[sessionurl_q]">$vbphrase[calendar]</a></td>
You want to replace the above code so it looks something like this:
Code:
<td class="vbmenu_control"><a href="YOUR DESTINATION HERE">NAVIGATION DISPLAY TEXT</a></td>
Here is an example of a link that says "Go to Google" that will forward people to Yahoo:
Code:
<td class="vbmenu_control"><a href="http://www.yahoo.com">Go to Google!</a></td>