In the Administrator Guide is an entire chapter on Workflow customization including example scripts.
What exactly is the functionality you want for the field you have created in the Test Case entity? Do you want it to be automatically filled in by pulling data from some related Requirement? Do you want it to present a list of BRD numbers from which the user will select, dynamically creating that list by looking at all the Requirements and what has been entered in the BRD NO fields there? I'm not clear about what you are actually trying to do. Perhaps if you provide a step by step example then you will get more specific responses.
Regardless, I believe that people learn best by experimentation, trial and error. So, review the product documentation, then try some experiments, then come back to the forum with the code you've written and specific information about how it isn't working the way you want.
What exactly is the functionality you want for the field you have created in the Test Case entity? Do you want it to be automatically filled in by pulling data from some related Requirement? Do you want it to present a list of BRD numbers from which the user will select, dynamically creating that list by looking at all the Requirements and what has been entered in the BRD NO fields there? I'm not clear about what you are actually trying to do. Perhaps if you provide a step by step example then you will get more specific responses.
Regardless, I believe that people learn best by experimentation, trial and error. So, review the product documentation, then try some experiments, then come back to the forum with the code you've written and specific information about how it isn't working the way you want.