Here's my really old TrimFront+Back.js script.

/**
 * This script will trim the front and back for all selected events.
 *
 * Written By: Edward Troxel
 * Copyright 2004 - JETDV Scripts
 * Modified: 08-03-2005
 **/

import System;
import System.IO;
import System.Windows.Forms;
import Sony.Vegas;

var trimAmt = new Timecode("00:00:01:00"); //Change this to be the trim amount

try {  //Go through the list of Tracks
  var trackEnum = new Enumerator(Vegas.Project.Tracks);
  while (!trackEnum.atEnd()) {
    var track : Track = Track(trackEnum.item());    //Go through the list of Events
    var eventEnum = new Enumerator(track.Events);
    while (!eventEnum.atEnd()) {
      var evnt : TrackEvent = TrackEvent(eventEnum.item());      if (evnt.Selected) {
        var dStart = evnt.Start + trimAmt;
        var dLength = evnt.Length;    //Get current take offset
    var tke = evnt.ActiveTake;
    var tkeoffset = tke.Offset;
    tkeoffset = tkeoffset + trimAmt;
        evnt.Start = dStart;
    tke.Offset = tkeoffset;
    
        dLength = dLength - trimAmt - trimAmt;
        evnt.Length = new Timecode(dLength);    
      }
      eventEnum.moveNext();
    }
    trackEnum.moveNext();
  }
} catch (e) {
    MessageBox.Show(e);
}