Prevent scrolling of parent element when inner element scroll position reaches top/bottom?

I have a little "floating tool box" - a div with position:fixed; overflow:auto. Works just fine.

But when scrolling inside that box (with the mouse wheel) and reaching the bottom OR top, the parent element "takes over" the "scroll request" : The document behind the tool box scrolls.
- Which is annoying and not what the user "asked for".

I'm using jQuery and thought I could stop this behaviour with event.stoppropagation():
$("#toolBox").scroll( function(event){ event.stoppropagation() });

It does enter the function, but still, propagation happens anyway (the document scrolls)
- It's surprisingly hard to search for this topic on SO (and Google), so I have to ask:
How to prevent propagation / bubbling of the scroll-event ?

Edit:
Working solution thanks to amustill (and Brandon Aaron for the mousewheel-plugin here:
https://github.com/brandonaaron/jquery-mousewheel/raw/master/jquery.mousewheel.js

$(".ToolPage").bind('mousewheel', function(e, d)  
    var t = $(this);
    if (d > 0 && t.scrollTop() === 0) {
        e.preventDefault();
    }
    else {
        if (d < 0 && (t.scrollTop() == t.get(0).scrollHeight - t.innerHeight())) {
            e.preventDefault();
        }
    }
});

It's possible with the use of Brandon Aaron's Mousewheel plugin.

Here's a demo: http://jsbin.com/jivutakama/edit?html,js,output

$(function() {

  var toolbox = $('#toolbox'),
      height = toolbox.height(),
      scrollHeight = toolbox.get(0).scrollHeight;

  toolbox.bind('mousewheel', function(e, d) {
    if((this.scrollTop === (scrollHeight - height) && d < 0) || (this.scrollTop === 0 && d > 0)) {
      e.preventDefault();
    }
  });

});