Edit samba user password hash/digest without knowing the password

I am maintaining a samba server for an office environment. So far, whenever there had to be a new user, I called the person over and let him type in his samba password on my console, after I typed smbpasswd -a username. I don't want to know any of the passwords. For the unix passwords, I just let them create a password digest (e.g. http://www.askapache.com/online-tools/htpasswd-generator/) in advance and edit the password file later with vipw -s. Now I have a remote colleague who can't come over to type in his password, but I still don't want to know it at all. How can I edit the samba password without actually knowing the password itself, but just a digest?