Help needed in blocking files in squid

[acarbinem1]

Hello

I am trying to block certain files from being downloaded on my network. I am trying to block the users from downloading Windows executables. The users of my network refuse to listen to me when I tell them not to download random programs from the net. I have tried many ways of configuring squid to block these files, I have tried editing the conf manually and even tried blocking the mime types with acls, but the users can still download the questionable files. I know there are many posts on this,but I cannot get this working.

Thanks