Scrolling - Detect If Already At The Bottom Of The IFrame

I have an iFrame that is 1024px X 700px. I removed the scrollbars using Scrolling="No" because the scrollbars don't look very pleasing to my eyes. I use javascript to scroll the iFrame but for the life of me, I cannot figure out how to detect if I'm already at the bottom of the iFrame. How can I detect if I'm at the end of the document in an iFrame so that I can scroll the parent window instead of the iFrame. TLDR: If document position is at the bottom of the iFrame, I want to scroll the parent window.

<script type="text/javascript">
function handle(delta) {
var d=delta*-10;
window.scrollBy(0,d);
}
function wheel(event){
var delta = 0;
[Code]...