php links in pages

I want to create a page in domain.com that has content and links that point to pages that are created by new blog template for each site, so the change but the post number stays the same.
eg domain.com/site1/wp-admin/post.php?post=111&action=edit
domain.com/site2/wp-admin/post.php?post=111&action=edit
etc.

How do I enter wp-admin/post.php?post=111&action=edit and have it direct to properly to each site?

Do I use this?
http://wordpress.org/extend/plugins/allow-php-in-posts-and-pages/
What php code do I enter to direct properly to the corresponding blog?

Is this a security issue?