looking for a way to detect scrolling to a bottom of a page

I was able to hook onto the window scrolling event and detect a scroll to the bottom of the page with the following code. However, I need to detect a scroll in a dialog object, and I am unable to hook onto the scroll event in the dialog. I think I'll post a new question for this issue, though I am guessing this might not have an straight forward solution.

window.onscroll = function() {
console.log("scrolling.....");
// @var int totalPageHeight
var totalPageHeight = document.body.scrollHeight;
console.log("totalPageHeight = " + totalPageHeight);

// @var int scrollPoint
var scrollPoint = window.scrollY + window.innerHeight;
console.log("scrollPoint = " + scrollPoint);

// check if we hit the bottom of the page
if(scrollPoint >= totalPageHeight){
console.log("at the bottomz");
data.isScrollBottom = true;
}
}