File extension in filereference

Question

How can I add a file extension when i download a file using FileReference?
Every time the save dialog box appears i get the filename, but not the file extension.
Any help?

Answer 1

For others if they would like to see:
set audEXT to {"mp4", "m4a", "mp3", "aif", "aiff", "wav", "m4r"}
property FoldersToMake : {"AUDIO", "VIDEOS", "Python workspace", "Documents", "PHOTOS", "Quartz Compositions", "Other"}
          tell application "Finder"
       repeat with newFolder in FoldersToMake
                                        try
                                                       make new folder of folder "CleanUP" with properties {name:"" & newFolder & ""}
                                        end try
                         end repeat
          end tell
          move (every file of desktop whose name extension is in audEXT) to the folder "AUDIO" of folder "Stuff"