Post Simultaneously to Main Post Page and SubPage

I am working on a book review blog. Would like to be able to post review on main post page but also have it post on sub page. For instance, book review given a 4 rating. Would like to have that post simultaneously on sub page that is specified for all book that have a 4 rating. In essence that subpage is an archive page that will make it easier for people to search. Is there a code I can place on the bottom of my post so it will automatically post on the sub page as well? Or do I just have to stop being lazy and just manually post the same review to my subpage? http://www.darkhavenbookreview.com is the site. I thank you for the help in advance.