So you want to upload only files that do not exist on the server?
Use synchronize remote -criteria=none c:\local\path /remote/path
See https://winscp.net/eng/docs/scriptcommand_synchronize

Hi,

I am using script, cmd to move file to the FTP. I dont want it to overwrite the file if its still on the FTP. Is this possible.

Thanks in advance,
Ash