Backup of network paths from windows...snapshot error



I have windows client installed on one of my computers and I need to make backups of some folders that are shared in other computer in which I can´t install client (for other reasons).
I added UNC path to the backup list and it is doing backups, but always generates errors about snapshot creation (which obviously is not possible over UNC). Is there any way to tell client to skip snapshot creation for some folders in windows?

Thanks a lot.