You can do following things:
1. The ASP which generates the report/Data file will generate a HTML file and will put it in a temp directory (Use file system objects for this).
2. Now from the ASP from which you have to send the file as attachment, execute the first file (using server.execute command) and then Use CDONTS to send that generated HTML file as attachment. After the mail send code, delete the HTML file.
Hope it will work for you.