Compare the 'login user name' and 'detected by' fields

Hi All,

Good Day !!

Kindly help with the below requirement.

We have user groups namely Development, Tester and Business. Apart from Tester role, other two groups should also be able to raise new defects. While raising defects, Severity & Priority are mandatory fields. 

The user who raised the defect should be able to edit Severity & Priority at any point of time. Other than the 'Detected By' user, no one should be able to edit these 2 fields. 
Hence I need to compare the 'login user name' and the 'detected by' fields. If both are same, I will set Severity & Priority fields as editable. Otherwise this would be set non-editable.

Any help is much appreciated.

Thanks,

Rarima..