How do I set samba permissions?

["Mark Wright" <mwright@pro-ns.net>]

I'm trying to use an NT editor to edit a bunch of perl scripts on my debian
server, shared through samba.  The problem is that the 'group execute'
permission keeps getting turned off when I save the file.  I've set create
mask to 0770, but every time I save a file, the permissions change
from -rwxrwx--- to -rwxrw----.

Here's the relevant part of my smb.conf:

[homes]
   comment = Home Directories
   browseable = no

; By default, the home directories are exported read only. Change next
;   parameter to "no" if you want to be able to write to them.
   read only = no

; File creation mask is set to 0700 for security reasons. If you want to
;   create files with group=rw permissions, set next parameter to 0775.
   create mask = 0770

; Directory creation mask is set to 0700 for security reasons. If you want
to
;   create dirs. with group=rw permissions, set next parameter to 0775.
   directory mask = 0770