member list addition

[steve71]

From the member list template:
<if condition="$show['reputationcol'] AND exec_switch_bg()"><td class="$bgclass">$userinfo[reputationdisplay]</td></if>


This is the related plugin:

if ($post['reputation'] != 0)
{
$post['average'] = vb_number_format($post['reputation'] / $post['posts'], 2);

How can I place the ['average'] to be included/sorted into the member list?