Currently Being ModeratedDec 6, 2012 4:30 AM (in response to Robzzzz)
Here is one way to do it.
For your Trailer, use the SHARE menu to SHARE/EXPORT USING QUICKTIME. Choose Movie to QuickTime Movie. Choose Apple INtermediate Codec as your codec. Save it where you can find it.
Now use FILE/IMPORT MOVIE to import this new finished trailer movie into your Event. Now you can drag it from your Event to your movie.