<p>I believe the question says it all ... (I'll update if needed)</p>

You aren't going to be able to have your site as non-SSL, with a login box on every page, and then submit the username and password via SSL.
The only way to really accomplish this is to use frames of some sort. This way your entire page could be non-SSL, but the login frame would have to be SSL.
The usual ways of doing this is to either lock down the entire site with SSL, don't worry about having the username and password SSL encrypted and go to SSL after they log in, or go the frame route I mentioned above.