[Plugin: Password Protect WordPress Blog] Submiting the password via an outside post.

We have a client that has a primary site under their domain and they have a wordpress blog under another. They would like to password protect the blog from random outside users, but would like the users of their site to click a button/link to log them in to the blog. With your plugin, is there a way for me to submit via hyperlink, form post/get, or any other means the password to the login this plugin creates? In looking at the code it didnt seem as though an outside submission would work but I wanted to verify that.

https://www.ads-software.com/extend/plugins/password-protect-wordpress-blog/