Using ftp wrapper in file_copy
I don't know what type of file are you trying to copy over the FTP server, but I did something like that once. This is what I did (it might give you an idea):


I created a content type where I added all the fields for the data I was collecting (like 10 fields)
Then I created an small module that will query the database and will create a CSV file from the data entered on the content type (I applied some logic to the data as well needed for my project)
I use the Drupal default file functions to name the file, placed on the define directory and avoid been overwritten by following exports.
Then on the same small module I created an small function that will read the directory content where the CSV file was and upload it to and FTP server.
When all this was done I use the "hook_cron" to create an small function that will do all that for me.


Note: in my project I created an small admin interfaced where I entered a couple of settings like the name and location of the local directory where the CSV files will be stored as well as the FTP credentials (the client wanted to have there as well) and the location on the FTP server as well.

Note 2: I know this module is good with moving media files: http://drupal.org/project/media_mover/

Thank you.