user/group creation privileges

I have a special question.
I'm about to make a system that is going to have several users are going to load
data with a web interface. This users are gonna be on a special group that will
have privileges on the database.
Now, I want to have on (or more) users to be able to create new users, put them
in this group and give them privileges to modify the database structure (SELECT,
INSERT, UPDATE, DELETE).
How can I do this last part? I didn't find much on the GRANT manual.

Saludos... :-)

System Administration: It's a dirty job,
but someone told I had to do it.
-----------------------------------------------------------------
Martín Marqués email: martin(at)math(dot)unl(dot)edu(dot)ar
Santa Fe - Argentina http://math.unl.edu.ar/~martin/
Administrador de sistemas en math.unl.edu.ar
-----------------------------------------------------------------