sudo under a defined directory

[meiemoehl at a1.net]

Hello!

How can I setup /etc/sudoers that a command like /bin/chmod can only work with 
superuser rights within a specified directory?

My /etc/sudoers:
---
Host_Alias WWW = 192.168.0.1

# User alias specification

# Cmnd alias specification
Cmnd_Alias CHOWN = /bin/chown
Cmnd_Alias CHGRP = /bin/chgrp
Cmnd_Alias CHMOD = /bin/chmod

# User privilege specification
root    ALL=(ALL) ALL
user1 WWW = NOPASSWD: CHOWN, CHGRP
user2 WWW = NOPASSWD: CHOWN, CHGRP, CHMOD
---

Thank you for help!!

bye,
Robert