Urgent:- Need to post Valued to "BG_TARGET_REL" and BG_DETECTED_IN_REL" for all the existing defects

Hi All,

I  need to post Values to "BG_TARGET_REL" and BG_DETECTED_IN_REL" for all the existing defects

Currently We are using a user defined field "ReleaseID" with user defined List for Releases,

now we want to use the system defined fields mentioned above,

so for all the existing defects we need to populate these fields for a value corresponding to the release it belong.

Thanks in Advance