post count in archive.php, category.php, etc

Hi all,

I’m having a bit of a pickle trying to customise the post count in my archives section (acrhive.php, plus category.php).

My front page is set to show 10 posts, but on archive pages I use the_excerpt and would like to show up to 20 posts on those pages..

I had saw another post which suggested doing this:

<?php query_posts('showposts=20'); ?>

which is fine, except it on monthly archives it starts showing the previous month’s posts!

I’m sure there must be a solution to this, hopefully a simple one, and I appreciate any help that can be offered from the WP community.

Thank you in advance,