So if I am reading you correctly, you want the link of the current page to not display based on a variable set in the URL. Is that correct?
So if your links are normally:
Home
About Us
Contact Us
Then if you are on the "contact us" section, you want it to only show:
Home
About Us
If that's the case, then say try something like this:
test.php?page=contactus
The links would go something like this:
<?php
IF(!ISSET($_GET['page']) || $_GET['page'] != "home") echo "<a href=\"test.php?page=home\">Home</a><BR />";
IF(!ISSET($_GET['page']) || $_GET['page'] != "aboutus") echo "<a href=\"test.php?page=aboutus\">About Us</a><BR />";
IF(!ISSET($_GET['page']) || $_GET['page'] != "contactus") echo "<a href=\"test.php?page=contactus\">Contact Us</a><BR />";
?>
If this isn't what you meant, I am sorry, I still don't get exactly what you are trying to do.