script for automatic daily downloading of data subscription files via FTP

I have a subscription to data files at NASA. Files are posted to my directory on their FTP server daily. I need to automatically download the data files with FTP but only those that I have not already downloaded. I think that a simple database or list file is needed to keep track of which files have been downloaded already. After the files have been downloaded, I process the files and move them to another folder. Therefore, my local folder will be emptied once a day and will contain no files before starting the download process. The FTP folder on NASA server will contain multiple files, some of which I have already downloaded but some may be new files that need to be downloaded. I prefer that the script is written in C# as my processing programs are written in C# but it could be written in any language that runs on a Windows 2008 Server. The downloading script needs to run once every day at a fixed time.