Hi
Once you have created your complete film save it as a VP project (.vpj file)
When you are ready to work with it, just load it into VP, select your start point and split the film. Now delete the left hand segment you don't need.
Proceed onto your stop point, split the film and delete the right hand portion that you don't require.
Now (if you want) save your segment with another name as another project.
Now save your segment as your movie.
Your original project will still be complete and you will have created a film from the bit you wanted.
Nat