receive files from remote site only if file does not exist in local directory

I need to only receive files via ftp when the file does not exist on my local machine. FIles are being added to the remote location on a weekly basis and they are being downloaded locally. I do not want to download all the files each time. Instead, just download what was not already downloaded. Is there a way to do this?  I want to do this using SSIS / ftp task.

Thanks in advance.