List posts in categories alphabetically

I saw another post which referenced this page:

http://jehiah.com/archive/wordpress-category-page-hacks

Which lets you put a snippet of code in wp-blog-header.php on line 345:

if ($whichcat)
{
$orderby = 'title';
$order = 'ASC';
}

But that doesn’t work in 1.5, it has a different coding layout. How can I get this to work in 1.5?