list of all user with his access but for admin

hi
summery of my problem:
i want have a middle admin but with user access for not read only field. for example i have field A ,field B.
field A is read only
field B can edit by user

if i get my middle admin access to backend , he can change field A through cb user managment menu. but i want he can not to edit that field A but can edit field B of all my users.
how to implement that?

You can't. There's no permission controls on a per-field basis. Read Only fields can always be edited from backend. I recommend just not giving backend access to users that can't be trusted to leave that field alone.