Posts per Page

Under Reading Settings > Blog Pages Show at Most, I would like for each blog page to show ALL the posts from one particular month. Therefore if I post 20 posts in September, it should show all 20 posts on the page but if I only posted 5 posts in August, only 5 should be displayed on the page. Is this possible and how would I have to go about making this work? I understand that it would be a coding thing rather than a plug into the settings field setup. Any help/suggestions would be much appreciated. Thanks in advance!