Auto master page application

Question

I wrote this script to see if I could hook master pages to a paragraph style and I have a couple of questions.
1. Currently I'm using the "onIdle" event type is there a better event type that could be used that would still run without interrupting the user?
I was thinking the "afterAttributeChanged" event type might work better. When is this one called? Is it called for every attribute change in the layout window?
2. I'm also searching for the pages that I want to change via grep and grabbing the page with paragraphs[i].parentTextFrames[0].parentPage;
Is this the most efficient way to do this?
Here's what I have so far:
#targetengine "session"
var doc = app.activeDocument;
var chapterStyleGroup = doc.paragraphStyleGroups.itemByName("Chapter");
var chapterTitle = chapterStyleGroup.paragraphStyles.itemByName("ChapterTitle");
var aMaster = doc.masterSpreads.itemByName("A-Master");
var cMaster = doc.masterSpreads.itemByName("C-Chapter Open");
var chapterPages = [];
app.findGrepPreferences = NothingEnum.nothing;
app.findGrepPreferences.appliedParagraphStyle = chapterTitle;
var paras = app.findGrep();
for (var i=0, l=paras.length; i<l; i++) {
          var parentPage = paras[i].parentTextFrames[0].parentPage;
          chapterPages.push(parentPage);
          parentPage.appliedMaster = cMaster;
var listenerTask = app.idleTasks.add({sleep: 5000});
listenerTask.addEventListener("onIdle", checkPages);
function checkPages() {
          var savedPrefs = app.findGrepPreferences.properties;
          app.findGrepPreferences = NothingEnum.nothing;
          app.findGrepPreferences.appliedParagraphStyle = chapterTitle;
          var paras = app.findGrep();
          for (var i=0, l=paras.length; i<l; i++) {
                    var parentPage = paras[i].parentTextFrames[0].parentPage;
                    if (chapterPages[i] !== parentPage) {
                              chapterPages[i].appliedMaster = aMaster;
                              parentPage.appliedMaster = cMaster;
                              chapterPages.splice(i,1,parentPage);
          app.findGrepPreferences.properties = savedPrefs;

Answer 1

Peter, without threading, the individual text boxes on the master page do number correctly. They are empty text boxes except for an invisible character such as a hard return, and once I have the invisible character in place, the numbers appear.
Because 1-6 already number and appear correctly, it doesn't make sense to me to thread them together, although I did try it including from caption 6 back to caption 1...this resulted in caption 1 disappearing and all the other captions reducing by increments of one (1-5).
I'm not sure if I'm 'placing' my list incorrectly (that term doesn't quite make sense to me ~ I thought you define a list and then apply it directly or through a paragraph style?) or what, but do you have any other suggestions?