Custom pages

[DAMINK]

I find i have to make a few custom pages on my site for whatever reason.
Now if i want to make a page viewable to members only i use below.

PHP Code:

<?php
include("global.php"); 

if ($vbulletin->userinfo['userid']!=0) { 
  echo "Welcome Back, <b>";  
  echo $vbulletin->userinfo['username'];
  echo "<br>";
    ?>

Blah blah blah

<?php
}
else {
echo "Go Away!";
}
?>

That seems to work ok.
How would i go about making this usergroup specific?