[Samba] File Permision Setup for Security

[updatemyself .]

Hai all,
 how i can avoid other users editing and deleting my files thats in samba
share...
there is more than 1000 users in my network
all users are authenticating to Windows2003 ADS,
 they cant delete others users files.. thats in samba but they can edit
it..spoil it
how i can avoid it...
 here is my corrent samba configuration
  [global]
 workgroup = MYDOMAIN
server string = Samba Server
log file = /var/log/samba/%m.log
max log size = 50
security = ads
encrypt passwords = yes
socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192
dns proxy = no
 #== Share Definitions ==#
#ldap idmap suffix = ou=emplist,dc=dqe,dc=com
password server = 172.16.20.200
realm = MYDOMAIN.COM
idmap uid = 16777216-33554431
idmap gid = 16777216-33554431
template shell = /bin/bash
template homedir = /home/%D/%U
allow trusted domains = no
idmap backend = idmap_rid:DQE=16777216-33554431
winbind use default domain = yes

[vol08]
path = /vol08_700
writable = yes
public = yes
nt acl support = yes
create mask = 0755
security mask = 0755
inherit permissions = yes
inherit acls = yes
force security mode = 0
directory security mask = 0777
force directory security mode = 0
 hope some one can help me.....
Thank You in Advance,
Jerrynikki.