Using apache or a .htaccess file for apache .
Order Deny,Allow
Deny from all
Allow from 123.45.6.7
You could create a link on say page 1 to page2 (located in a subdirectory with the .htaccess file in it) .. then when the link is clicked, you are either denied by the apache server or allowed in. The above lets ip address 123.45.6.7 pass to page 2 ..... all other ip addresses are denied access.
This assumes of course that you use the APACHE web server
HTH's