Add effects to clip in timeline - CS4

Ok I'm going to try to explain this the best I can

I have a full clip that I imported in. Half of the clip is showing 1 of 2 footage.. I cut the clip in half in the time line and left the original alone in the top left workspace where you import the clips.. In the time line I put both halves next to each other to show them simultaneously next to each other.. So an example would be One full clip - first half is someone pressing the gas pedal then  stopped the tape and taped the RPMs in the dashboard .. I put both of these next to each other to show the harder the pedal is pressed the higher the RPMs go (By the way this is an easy example what i really tapped would be way to hard and complex to explain )

So here is the thing .. I want to blur something out of the 2nd half of the footage.. I found a great example here .. This works but it does it in ref to the original clip that I left alone ... not to the won i chopped into pieces and moved around to get the timing right of when the gas pedal is pressed and the RPM's going .. I wanted to know if there was a way to just edit the piece that is in the timeline without modifying the original clip...

I hope i explained it well enough.. if not let me know and I will try to explain in further detail...

-rico