The best way to get an answer to your question is to post a sample workbook for the community to look at.
That said, I think that the answer lies in using MIN(Date). This will only show the date that the event first occurred.
I'm not sure exactly how to apply it to your view or calcs however, and a sample workbook will be the best way to help us help you.
Thanks Nicholas. This is proprietary information, but i will try and create a mock up.
Nicholas' has given some good advice, a mock up would be very helpful.
Even some fake data in Excel which demos the problem
That said, you question reminded of something i did for someone recently
its not exactly the same as your situation, but either MIN(), FIRST() and/or using LOD expressions (you need v9) will most likely be your answer.
Best of luck!