How to give edit permission only to specific fields in node edit in? I have content type with some cck fields:

- task time
- task status
- task executor
- task category


and of course title/body and other drupal node default fields.

each node of this content type will be assigned to a user selected from site users in task executor field.

I want the when the executor logins view all fields of assigned to task(node) but only can change (edit) the value of task status field. node edit doesn't do that.

I try to use 'Content Permissions' of cck module but it is not what I really need. it doesn't have control on title and body field and also the user can only see the fields he has edit permission on them in node edit page.

What can I do?

I hope I could explain my question clearly. 

Thank you.
You can use the Field Permissions module. It allows you to set permission for each field for every user type. It works simply fine.


  The Field Permissions module allows site administrators to set field-level permissions to edit, view and create fields on any entity.
  
  Features
  
  
  Enable field permissions on any entity, not just nodes.
  Role-based field permissions allowing different viewing patterned based on what access the user has.
  Author-level permissions allow viewing and editing of fields based on who the entity owner is.
  Permissions for each field are not enabled by default. Instead, administrators can enable these permissions explicitly for the fields where this feature is needed.