ok, so I understood right
You can use ssh and rsync on windows platform. They are not an exclusive *nix tool anymore.
but, if you really want to use samba, you can use smbclient to copy files from your Windows server to CentOS. Something like that:
smbclient //ip_of_win_server/bkp_share password -U username -W your_workgroup <<EOC
On windows/firewall you need to open the 137/139 ports, and create a specific share where the backups are.
There is no need to setup a SAMBA server on CentOS to do that.
This setup is weak from the security point of view. The transfer it is not encrypted, neither opening that specific windows ports for the world is a wise thing to do, but, well, it works for sure. I use this on my internal network to transfer files from a W2K machine to the tape backup server.