limiting connections

[Carlos Manuel Trepeu Pupo <charlie.mtp@xxxxxxxxx>]

I need to block each user to make just one connection to download
specific extension files, but I dont know how to tell that can make
just one connection to each file and not just one connection to every
file with this extension.

i.e:
www.google.com #All connection that required
www.any.domain.com/my_file.rar #just one connection to that file
www.other.domain.net/other_file.iso #just connection to this file
www.other_domain1.com/other_file1.rar #just one connection to that file

I hope you understand me and can help me, I have my boss hurrying me !!!