fetch the file name before downloading it
===

I'm downloading an ePub file from a URL.

Now I want to implement a mechanism by which if user tries to re-download the same file, he should get warning/error message and that file **should not be** downloaded again.

To implement this, I need to check the name of the file present in my library with the name of the file user is trying to download.

But I just have [this download link][1], and not the file name.

How to get the name of the file before download in order to compare it with the existing file?

[1]:http://dl.dropbox.com/u/1177388/flagship_july_4_2010_flying_island_press.epub

Any help appreciated...