Make CRM 2013 SubGrid as Readonly only on specific conditions through Plugin/Ribbon Customisations

Hi,

    I have a requirement to make a subgrid as readonly based on the status for specific set of users and specific to that record as well - CRM 2013

 (i) Status="Something" -  To make a subgrid as editable,Addnew,Add associated  in for all users specific to that parent record. 

 (ii)Status="Something" - 

        Users(A) - To make a subgrid as non editable,Should not add new, Should not add associated records only for that parent record . But the same user should be another create new main parent record and be able to add new Subgrid,Edit and Add associated Records. 

        Users(B)  - But still it should be editable,Addnew, Add Associated records .

  (iii) Status ="Something" - 

      For All Users - That Subgrid needs to be read only only for that parent record. If they create a new parent record, It should be allowed to add or edit Subgrid records      

 I tried to create an update plugin for associate and dissociate security roles on Status update. But that make all the other records as Read only or Editable as well. This is not working with Record Level, It works only on Entity Level.

 Any suggestions 

Thanks