While loading the page, inside page load, check the previous page URL with the below code.
Request.UrlReferrer
Quote:
HTTP_REFERER Returns a string containing the URL of the page that referred the request to the current page using an tag. If the page is redirected, HTTP_REFERER is empty
Compare the URL with the page where you have the links.
So, if it matches, then allow. Otherwise, redirect to where ever you want.