You can trim any clip in the Edit stage and then create a new movie.
However, you do not really have to do this in this instance. This is because it is not the DV-AVI file that will be written to the DVD.
When you get to the DVD Authoring Stage ULead will convert your AVI to a DVD compliant MPEG file. By the sounds of it your movie is in the order of about 20 minutes long. So even at maximum bit rate you will fit this on a single DVD quite comfortably.
COMPAQ something or other with 500Gb Boot Disk, 1Tb external Firewire Disk, 4Gb Memory and a super duper sound card, 19" TFT Monitor etc etc etc
Sony TRV33e : Sony TRV310e : Canon XM2
Sony Vegas Studio editions to v11
Remember, there is always more to learn than there is to teach.