Page object

Question

Hi all,
I've just started messing with InDesign scripting, and being a web developer I've obviously chosen to go with Javascript as my scripting language.  I had been reading through the available literature and thought I had pretty much figured out the DOM, and writing the script I was after.
The idea is, I've got 4 columns when the data flows top to bottom, left to right.  The function I wrote was supposed to add a textFrame to a page after first calculating how many frames are already on this page.  If it already contains 4 textFrames then it creates a new page, then puts the textFrame on that page.
The issue I'm facing is that it works fine for page 1, and page 2... but when it adds a page to a spread (in this case, page 3), the page object returned (even when access the last page of the document independently app.activeDocument.pages[-1]), it is return the page 2 object... so putting the textFrame on this page.
Below is my code.
function addTextFrame()
    var page = app.activeDocument.pages[-1];
    var thisPageFrames = page.textFrames.length;
    var columns = 4;
    if ( thisPageFrames == columns) {
        page = app.activeDocument.pages.add();
        thisPageFrames = 0;
    var thisFrame = thisPageFrames + 1;
    var leftMargin = page.marginPreferences.left;
    var rightMargin = page.marginPreferences.right;
    var topMargin = page.marginPreferences.top;
    var bottomMargin = page.marginPreferences.bottom;
    var pageHeight = app.activeDocument.documentPreferences.pageHeight;
    var pageWidth = app.activeDocument.documentPreferences.pageWidth;
    var frameHeight = pageHeight - topMargin - bottomMargin;
    var frameWidth = (pageWidth - leftMargin - rightMargin) / columns;
    var frameRight = (thisFrame * frameWidth) + leftMargin;
    var frameBottom = frameHeight + topMargin;
    var frameTop = topMargin;
    var frameLeft = leftMargin;
    if (thisPageFrames != 0) {
        frameLeft += (thisPageFrames) * frameWidth;
    var newFrame = page.textFrames.add();
    newFrame.geometricBounds = [frameTop, frameLeft, frameBottom, frameRight];
    return page;
addTextFrame();
Any advice you can provide would help me soooo very much.

Answer 1

I've got a further question... of course.
These XML documents will be served from a web server.  To ensure that people don't have multiple copies of these files on their machines, I've attempted to set up a script that will automatically import the XML document from a given URL each time it is activated.
I'm able to manually open the file by using: -
var xmlFile = File('Path/to/file.xml');
However, doing the same with a URI in place of the local path returns nothing.
var xmlFile = File('http://www.path.com/to/yourXML.xml');
Any ideas?