Detect user download

Soppose I develop a client web app (I don't have access to server code), Is it possible to detect when user downloads a file? I need something like:

//fires when user download file
function downloadFileCreated(obj){
    alert(obj.url); // prints the download link
}

here they assume that I have access to server code (but I don't have)

(I'm working on InternetExplorer add-on and I want to inject script that listening to user download)

Solution

How about using Google analytics like mentioned in below post?