[Samba] How do I lock a shared file?

[steve]

4.0.9 as a file server
Hi
We have a rw folder where we can share files. If a user opens a file, I
would like it to be locked so the other users can't open and edit it at
the same time.

Is this possible?

Here is the share with its acl:

[privado]
path = /home/privado
read only = No
inherit acls = Yes

getfacl /home/privado
getfacl: Removing leading '/' from absolute path names
# file: home/privado
# owner: root
# group: Domain\040Users
user::rwx
group::rwx
other::r-x
default:user::rwx
default:group::rwx
default:other::---

Cheers,
Steve