remove specific category from monthly archive

[suepreme 0]

I've tried to recreate this by adding add_action('pagelines_before_theloop', 'archive_exclude'); function archive_exclude() { if(is_monthly()) { query_posts('cat=-38,-31,-32,-33,-37,-51&posts_per_page=20'); } } but when I do this, my monthly archives all show the same posts, despite the fact that they haven't all been published in the same month. I get the same behavior when I use is_archive() instead of is_month(). Do you have an idea of how to solve this?