Good job with that trick... it's actually pretty cool.
Oasis trick is pretty simple.
When you register to take the USMLE ... lets say step 1 and then you take the exam and wait for the score. While you are waiting... if you attempt to register for the exam you will get a red screen saying you have taken the exam and awaiting results... but...
When the results are finished it takes them 5 days or so to mail it out.. i believe they mail it every friday or something. So what you could do is log on Oasis and try to reregister for the exam.. if it allows you to go into the reregistering area... then you failed... otherwise it will tell you that you may not retake the exam because you already took the exam etc etc etc. (it wont tell you the score obviously).
All this does is just tell you whether you passed or failed 5 days ahead of time... no biggie.