This script will take a text layer with multiple lines, and create a new range selector.  It will create keyframes that incrementally select each line of text.  We use this a lot for animating lists and things.  You can than easily apply properties to the selector.

/*********************************************/

// make sure a comp is selected
var activeItem = app.project.activeItem;
if (activeItem == null || !(activeItem instanceof CompItem))
 {
  alert("You need to select a layer before running this script");
 }
else
 {
 // make sure at least one layer is selected
 var selectedLayers = activeItem.selectedLayers;
 if (selectedLayers.length != 1 )
  {
   alert("Select one layer before running this script.");
  }
 else
  {
  app.beginUndoGroup("Create Text Selector");
  
  
  for(i=0; i<selectedLayers.length; i++)
  {
   //If Text layer
   var theTextLayer = selectedLayers[i];  
   
   CreateTextSelector(theTextLayer);   
  }
   
  app.endUndoGroup(); 
   
  }
 }
 
function CreateTextSelector(theTextLayer)
{
 var lineCount = 1;
 var layerText = String(theTextLayer.text.sourceText.value);
 
 for(i=0; i<=layerText.length; i++)
 {
  if(layerText.charCodeAt(i) == 13)
   lineCount++;
 }
 
  var theTextProperties = theTextLayer.property("ADBE Text Properties");
  
  var theAnimators = theTextProperties.property("ADBE Text Animators");

  // add a Text Animator property to control the highlight style
  var highlightAnimator = theAnimators.addProperty("ADBE Text Animator");

  var highlightSelectors = highlightAnimator.property("ADBE Text Selectors");

  // add a Range Selector property to control the highlight timing
  var highlightSelector = highlightSelectors.addProperty("ADBE Text Selector");

  // define the range selector's Advanced (7) property group
  var advancedSelector = highlightSelector.property("ADBE Text Range Advanced");

  // define the Advanced property group's Unit (1) property and set to Index (percentage = 1, index = 2)
  var unitsProperty = advancedSelector.property("ADBE Text Range Units");
  unitsProperty.setValue(2);
  
  // base sur ligne
  var basedOnProperty = advancedSelector.property("ADBE Text Range Type2");
  basedOnProperty.setValue(4);

  // define the range selector's Start (4) and End (5) properties and set both to zero
  var rangeStartProp = highlightSelector.property("ADBE Text Index Start");
  var rangeEndProp = highlightSelector.property("ADBE Text Index End");

  var animLength = .5;
  var animSpacing = 2;
 
  for(j=0; j<lineCount; j++)
  {
   var inPoint = theTextLayer.inPoint + (animSpacing * j);
   var outPoint = theTextLayer.inPoint + animLength+(animSpacing * j);
   
    startKey = rangeStartProp.addKey(inPoint);
    rangeStartProp.setValueAtKey(startKey, (j<1)?(0)j-1));
    
    startKey2 = rangeStartProp.addKey(inPoint+animLength);
    rangeStartProp.setValueAtKey(startKey2, j); 
       
    endKey = rangeEndProp.addKey(inPoint);
    rangeEndProp.setValueAtKey(endKey, j); 

    endKey2 = rangeEndProp.addKey(inPoint+animLength);
    rangeEndProp.setValueAtKey(endKey2, j+1);
  }
}
 
function SetKey(myLayer)
{
 opacProp = myLayer.property("Opacity");
 inPoint = myLayer.time;
 outPoint = inPoint + .5;
 
 var startVal = 100;
 if(opacProp.numKeys > 0)
  startVal = opacProp.value;
 
 inKey = opacProp.addKey(inPoint);
 opacProp.setValueAtKey(inKey, startVal);
 outKey = opacProp.addKey(outPoint);
 opacProp.setValueAtKey(outKey, 0);

}