I've asked around, and received a number of qualifying questions from senior support engineers. In summary, though, they suggested that your best bet in this case is to contact customer service. Alternatively, if you could elaborate:
Thanks for your response.
1. I would like to set "Test Result" fields in general read only.(It has to edit only through trigger).
2. I has to set globally.
Unfortunately, Test Result Fields do not directly support the concept of Editability. You could impose editability limits through the use of trigger scripts.
If this is an important feature to you, please contact Integrity Support to have an SPR created. (An SPR, or Software Performance Report, is equivalent to what MKS called an RFC, or Request for Change).