Help: Customise the poster name formating in regard to usergroupid

I've hacked the formating of in 'who's online', 'member list', and homepage's 'currently active users' so moderators and admins are shown in a different color.

I now which to do the same in the forum vies and tread view but I can't find where I need to edit the code.

As an example, in forumdisplay.php I changed

$username = $forumuser['username'];

with the following:

if ($forumuser['usergroupid'] == 6 or $forumuser['usergroupid'] == 9) {
$username = "<b><font color=\"EED500\">$forumuser[username]</font></b>";
} else if ($forumuser['usergroupid'] == 5 or $forumuser['usergroupid'] == 7) {
$username = "<b><font color=\"A0A0A0\">$forumuser[username]</font></b>";
} else {
$username = "<b><font color=\"FFFFFF\">$forumuser[username]</font></b>";
}

(Sorry for the lack of indentation but I don't know how you guys do to make formating in a quote...)

Can anyone help me with this?
And by the way, I do not require a complete hack, I just need a hint on where I should look to insert my modifications.

Thanks

[skerjean]

Already got to try this technique a couple of time. I must be on the good track.