How Do I Detect File Download Being Cancelled?

I have a file download queue consisting of a SQL Server Table holding details of the files in the queue, and a download folder where the actual file resides.

The table is gone through to list for the user all files available for download (ie. all files not marked for deletion). The User selectes one, the file is downloaded using ASP

(ie. required headers are written to the Response object, followed by the file contents - so that the browser initiates the file download process rather than trying to parse/display the file), the sql table is updated to mark the file for deletion (the actual file is deleted by a separate process running on the server), and the list presented to the user is updated. Code: