Jeg fandt flg dokumentation på Nettet
   lngFileNum = FreeFile
   Open strFileName For Binary As lngFileNum
   lngFileSize = LOF(lngFileNum)
    ReDim bytFileContent(lngFileSize)
    Get lngFileNum, 1, bytFileContent
    Close lngFileNum
    strDownloadFileName = Right$(strFileName, Len(strFileName) - InStrRev(strFileName, \"\\\"))
     Response.Buffer = True
    Response.ContentType = \"application/octet-stream\"
    Response.AddHeader \"Content-Disposition\", \"attachment; FileName = \" & _
                        strDownloadFileName
    Response.AddHeader \"Content-Length\", lngFileSize
    Response.AddHeader \"Document\", strDownloadFileName
    Response.AddHeader \"Script_Name\", strDownloadFileName
    Response.BinaryWrite bytFileContent 
http://www.aspwatch.com/c/200037/d712E66F68B7A11D4AEF700A0C9E95208.asp