help writing simple plugin

[aebstract]

Okay I have this code:

$result = mysql_query("SELECT COUNT(userid) FROM userban WHERE adminid = '1'") or die(mysql_error());
while($r=mysql_fetch_array($result)) {

vB_Template::preRegister('header', array('bancount' => $r['userid']));

}

I place it in my template like:

{vb:raw bancount}

Product: vbulletin
Hook Location: global_start



It's not displaying a number or any error on the page at all. I was trying global_start as per your suggestion but is there some sort of method I need to be using to try and find the correct hook location or is this a problem with how the code is written?