[Zope] Add an existing role to an existing user via dtml methods

[paul_s_johnson@urscorp.com]

I am trying to create some user management pages for site administrators
(non-programmer types).  How do I programmatically add an existing role to
an existing user via dtml?

I searched the archives with no success.  Using Zope 2.2.2 on Linux.

P. Johnson