Changes allowed on some metadata only

[silgar]

We need, under certain conditions, to prevent changes to some metadata, while allowing modifications to the other metadata.
We are using Alfresco Share 3.4.d Community.
We have a custom content (documentci) specializing cm:content.
We added aspects and properties to documentci.
We want to restrict modifications to a subset of metadata depending on the value of a property (the state of the document).
How could we implement this?

[mrogers]

You can use forms to make certain fields display read only.   

Its not really property level permissions but it is better than nothing.

[silgar]

Thanks!
Following your suggestion we have to implement theese steps:

1) create in share-config-custom.xml a new form for "custom:documentci" type,
     with modifiable and read-only fields as we need (ok, we know how to do it)

2) add a new custom action "Edit Metadata" in the right-side list of actions in the document details view (ok).
    The new action will be displayed depending on the value of document property "custom:state".  
    We can define new 'evaluators' in the file:
    \alfresco\WEB-INF\classes\alfresco\templates\webscripts\org\alfresco\slingshot\documentlibrary\evaluator.lib.js

       if ( node.properties["custom:state"]=="Approved" )  {
               permissions["edit-approved"] = true;
       } else  {
               permissions["edit-notapproved"] = true;
       }

    and modify the file
    \share\WEB-INF\classes\alfresco\site-webscripts\org\alfresco\components\document-details\repo-document-actions.get.config.xml

    adding the new "Edit Metadata" action that will open the new form, and changing the permission of out-of-the-box  "Edit Metadata" action:

    <actionSet id="document">
        …..
       <action type="simple-link" id="onActionDetails" permission="edit-properties,edit-notapproved" href="{editMetadataUrl}"
                   label="actions.document.edit-metadata" />
       <action type="simple-link" id="onActionDetails" permission="edit-properties,edit-approved" href="????????"
                   label="actions.document.edit-metadata" />   
    </actionSet>


>>> We don't know how to call the new form when the user clicks the new custom "Edit Matadata" action.

Could you please help us with this point?