Render 404 file not found when going to some pages from one domain but allow access from another?

[Andy B]

I have some pages in a folder of my web application that I want to return a
404 file not found error for when people try to navigate to them through
www.eternityrecords.org domain name. On the other hand, I want to allow
access to these pages if people are going to www.inhim.eternityrecords.org.
How would I do something like this?