I have setup SLA for the ticket create option so now whenever any new ticket is generated 8 business hours respond time will be allocated to the ticket . But the problem is when client is reply to the ticket then no due date or response  time will be allocated to the ticket. I want to set up the response time for the ticket reply or customer reply option too . I have tried to setup this option but its calculating the 8 hours time from the ticket created time . It needs to be calculated from the customer reply time..

Please tell me how to do this