custom header for a category. Mandigo Theme

Hi there,
I’ve trying to do this without good results.
I’m trying to put a custom Header image to a specific category on my wordpress 2.61 using Mandigo theme.

I’ve tryed this on the style.css.php file.

<?php if (!isset($_GET[‘noheaderimg’])): ?>
background: url(‘schemes/<?php echo $mandigo_scheme; ?><? if (is_category(‘8’) || in_category(‘8’)) echo “/images/headev”; else echo “/images/head”; ?><?php echo ($mandigo_1024 ? ‘-1024′ : ”); ?>.jpg’) bottom center no-repeat;
<?php endif; ?>

(my code is in bold style)
headev.jpg is my custom header image for that category.
Mandigo readme says how to doit for a page (and works great), but I’ve been not able to do it for a category.

Thanks for any help.
Sergio.