If you have Samba, you don't need ftp. If you don't have Samba, how can you monitor the share? Are you trying to find out how to see the Windows share so you can monitor it, or are you trying to figure out how to periodically monitor something which you can already see? Anyway, smbclient or an SMB / CIFS mount is probably the crucial piece of infrastructure you need in order to get going.
Code:
while true; do
cp /path/to/ugly/samba/share/name/"ugly windows file name here" /path/to/unix/file_name.xls && break
sleep 300
done
