How to block specific URL instead of whole domain
i'm sorry to tell you, it wont work.

In the hostfile you can only set an IP-Adress of an domain manually.
For example:
I dont want that my pc always looks for IP-Adress for ilovethis.net.

Or a better one:
I have many photos, videos and audio on my homeserver. But i dont want to always type 192.168.178.178 (etc.) in my Browser. 
Yes! I would add an entry to my hostfile which says: Domain home.server should go to 192.168.178.178 (looks like: 192.168.178.178 home.server)

I hope you know what i mean.
This was not made for specific url,
its for local DNS manipulation.

Greetings,
Fischmaster