Filter Taxonomy reference field on Workbench Access permission i need some help with Workbench access based on taxonomy.

This is my use case:
I have this taxonomy structure for my site:
 - Term A
 - Term B
 - Term C

And i have 2 roles:
 - editor
 - editor C

Editor c users must be able to create or update only the term C nodes.

I installed Workbench, Workbench Access and Field Property to control this behavior.
I configured Workbench Access on Taxonomy.
In admin/config/workbench/access/roles i put Roles “Editor C” only in “Term C” Section. 

I created in each content type a Taxonomy Reference field, based on Workbench Access (i checked “Workbench Access control field”).
So this fields has two purposes:
 - tagging the node on my taxonomy structure
 - Assign the proper editorial group

The problem:
When an Editor C user adds a content, he can select any term value, not only “Term C”.
In other words the  Taxonomy Reference field display all result.

How can i filter/limit the record of taxonomy reference on workbench access permission?

P.S.
If i check “Require a Workbench Access form element” in admin/config/workbench/access/settings the module add a “core” access control field in each content type.
This fields are filtered on Workbench access permission but i loose my first purpose (tagging the node on my taxonomy structure).

Can anyone help me?
Thanks in advance,
Matteo
You must install Taxonomy Access Control module. Follow this steps:

1) Enable the module.

2) Go to admin/config/people/taxonomy_access

3) Click configure link for role "editor"

4) Click "Add vocabulary" link. Then select the vocabulary where you have terms "Term A", "Term B" and "Term C" and press "Add" button.

5) Click "Add term" link. Select "Term A". Configure permissions for this role and term (you should select "Allow" in every case). Once done press "Add" button.

6) Do the same for Term B

7) Do the same for Term C, but this time select "Deny" in every case.

8) Press button "Save all"

9) Go to previous window and do the same but this time for role "editor c". However you have to do the opposite: Terms A and B should have "Deny" in every case and Term B should have "Allow" in every case.

I hope this helps you! If it doesn't, you should checkout the Organic Groups module too. In case you need Organic Groups notice you also have OG Vocabulary module.