customize the actions button in detailview

Hello everyOne.
I want to know how can i custom the actions button in detailview.
In this moment my action_menu btn of Contract module is look like:
actionBtnDetailView_EN.PNG
So my need :
- Hide viewChange_log btn for all users EXCEPT ADMIN
- if (status_ctr == 'Signed'){
               hide edit btn;
               hide delete btn;
   }

Thank u for ur help