There are some ripping programs, that might allow you to extract just portions, but they will require work. There are some links to ripping software in this ARTICLE. I have no direct recs. As I have both a DVD player and an A-D bridge, I would just play the DVD, and cue it up, then Capture that portion. I think that a program along the lines of "VideoReDo" might be useful. Others will likely have some direct program recs. for you.
If one does not have an A-D bridge, then it is probably just easier to Import the VOB's that contain the footage (remember, a VOB can only hold ~ 1GB of material, so the enclosed MPEG files might span more than one VOB. Then, Trim that material in the Capture Project, Export/Share from that Project, and Delete all of the Capture Project and its Assets.
Since you are dealing with MPEG-2 materials, my first choice for that Export would be something like the Lagarith Lossless CODEC, or to DV-AVI.