Hi , thanks Fred , thank you very much , following your instruction i have just completed the task.

Hi ,thanks for your reply. Can u please elaborate this as i am very new to salesforce , thanks in Advance

Hi , Through workflow it is working. But the problem is suppose in our case status picklist there is 10 value. For that Case i need to create 10 different work flow rules. So i think trigger is the good option. Sir I have written a trigger. But cannot solve the error. Please see the trigger and ahelp me to solve this

Thank you so much ..... Its working....Through workflow rule. But there i am facing a small problem , When i am substacting two Date/Time field it should return the time. But i only get the Number of days. Not getting the time. "LastModifiedDate-CreateDate"... Like it return only a number like 15....Created By Staurt Roz, 9/3/2015 7:09 AM, Last Modified By Staurt Roz, 9/18/2015 4:53 AM.. It returns only 15 , but not returning the min and hour........

Hi , Thanks for replying. I am very new to salesforce. I work with workflow as well. But i am facing difficulty . Can you kindly elaborate the process what u suggest... thanks in Advance.