if conditionals php

[CoffeeLovesYou]

Hi..
I have a question.

When using PHP and global.php, we can use conditionals like:

PHP Code:

<?php
if ($vbulletin->userinfo['usergroupid'] == '6' )
    {
    echo "Hello";
             } else {
             echo "You do not have permission for this page"; }
    ?>

However..
Is it possible to do this with user fields?
E.g.

PHP Code:

<?php
if ($vbulletin->userfield['field8'] == 'Yes' )
    {
    echo "Hello";
             } else {
             echo "You do not have permission for this page"; }
    ?>

So basically, if their userfield field8 value is 'Yes', they can see whatever..