I have created a new side box called reward_points

I want this side box to only appear on select category pages.

I have read the tips and copied the "featured" example to do so, but I cannot get it to work. The side box still appears on every page.

in includes/modules/sideboxes/my_template/reward_points.php
i added:

if ($this_is_home_page) {
$flag_disable_left = true;
}

but nothing! Any suggestion?