Okay. Here you go for the long answer:
Every Test Suite and test case has something called setup script and tear down script. Both are groovy scripts which as the name suggests are run before and after the running of test suite/case respectively. If you open test suite by double clicking it, look for "setup" right above where you would get log. The editable area is too less so you will have to expand it. This setup script on a test suite level will can set properties at all 400 test cases level from a for loop since all these test cases would probably be under this same test suite. Does that make more sense?
Regards,
Deepesh
