Hi again.
I thought I would work it through myself, then had other things to attend to, now back on this:
I have read the link above many many many tomes before and after link was referenced.
Can not for the life of me work out what I am doing wrong.
FIELD 1:
SELECT a.name AS value, a.name AS text
FROM #__users AS a
INNER JOIN
#__user_usergroup_map AS b
ON b.user_id = a.id
WHERE b.group_id = 10
OPTIONS VALUE: a.name
This produces my list of users. Nice.
FIELD 2:
SELECT a.id AS value, a.id AS text
FROM #__users AS a
WHERE a.name = [parent]
PARENT: a.name
Is it OPTIONS VALUE?
Is it PARENT?
Out of ideas except for my trusty sledgehammer