Who's Online...where can I find the "$activeusers" code?

I'm planning a hack that adds a specific image for a purpose to each username that is in the Currently Active Users: screen on the index page...but I cannot find where I need to add the code. I found $activeusers in one of the templates, but then I searched for the code for that in some of the php files but I couldn't find it...anyone know where I could find it?

[Admin]

In index.php:

$activeusers = "";
$loggedinusers = "";
if ($displayloggedin) {
  $datecut=time()-$cookietimeout;
[high][... etc ...][/high]
  $recordusers = $maxusers[0];
  $recorddate = vbdate($dateformat,$maxusers[1]);
  $recordtime = vbdate($timeformat,$maxusers[1]);
  eval("\$loggedinusers = \"".gettemplate('forumhome_loggedinusers')."\";");
}