Make a field read only and do the chnage while some code is running for that field

Hello all,

I have added a button in the ribbon area of a customize form .on that button click i want to change the "status reason" field value from "active" to "resolved" .but i am able to make the changes in the fie;d only in the following case:-

when my field "status reason" is in edit mode, is i change my field to read only behaviour then i am not able to do the change in the field "status reason".

So ,I want a solution how i can change the status reason of the field while making the field  "read only".

i am using Microsoft dynamics CRM 2011 on premise,and i have used Ribbon workbench for developing a button and doing the above work.

Thanks