Samba - Password protect write
I am running Samba 3.4.7 on Ubuntu 10.4 LTS. I have some shares setup between my samba server and some windows machines. I have figured out the permissions to deny certain machines write access to certain folders but I am looking to simply password protect writing to these files. I want all computers to be able to read what I share (I have this setup now) but for a few folders I want them to be prompted for a password if they try to modify the contents (the part I need help with). Does anybody have any suggestions? What other information is needed?