Hide custom fields by usergroup?

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Can someone give me a hand in creating a small plugin for vB 3.8.7? I want to hide/show the custom profile fields in usercp/editprofile by usergroup.

I guess the plugin should look something like this:

if (!is_member_of($vbulletin->userinfo, array(X, Y, Z)))
{
    unset(
        $vbulletin->cfield['1'],
        $vbulletin->cfield['2'],
        $vbulletin->cfield['3']
    );
}

Any help/advice would be appreciated.