function drag(elementToDrag, event, elementToScroll) {
	var topBoundary = 0;
	var bottomBoundary = topBoundary + elementToDrag.parentNode.clientHeight;
	var elementHeight = elementToDrag.clientHeight;
    var startY = event.clientY;    
    var origY = elementToDrag.offsetTop;
    var deltaY = startY - origY;
    var scrollClient = document.getElementById(elementToScroll);
	//alert ('scrollbar height: ' + elementHeight + '\r\nbottom boundary: ' + bottomBoundary + '\r\nlistbox height: ' + scrollClient.clientHeight);

    // Register the event handlers that will respond to the mousemove events
    // and the mouseup event that follow this mousedown event.  
    if (document.addEventListener) {  // DOM Level 2 event model
        // Register capturing event handlers
        document.addEventListener("mousemove", moveHandler, true);
        document.addEventListener("mouseup", upHandler, true);
    }
    else if (document.attachEvent) {  // IE 5+ Event Model
        // In the IE event model, we capture events by calling
        // setCapture() on the element to capture them.
        elementToDrag.setCapture();
        elementToDrag.attachEvent("onmousemove", moveHandler);
        elementToDrag.attachEvent("onmouseup", upHandler);
        // Treat loss of mouse capture as a mouseup event
        elementToDrag.attachEvent("onlosecapture", upHandler);
    }
    else {  // IE 4 Event Model
        // In IE 4 we can't use attachEvent() or setCapture(), so we set
        // event handlers directly on the document object and hope that the
        // mouse events we need will bubble up.  
        var oldmovehandler = document.onmousemove; // used by upHandler() 
        var olduphandler = document.onmouseup;
        document.onmousemove = moveHandler;
        document.onmouseup = upHandler;
    }

    // We've handled this event. Don't let anybody else see it.  
    if (event.stopPropagation) event.stopPropagation();  // DOM Level 2
    else event.cancelBubble = true;                      // IE

    // Now prevent any default action.
    if (event.preventDefault) event.preventDefault();   // DOM Level 2
    else event.returnValue = false;                     // IE

    /**
     * This is the handler that captures mousemove events when an element
     * is being dragged. It is responsible for moving the element.
     **/
    function moveHandler(e) {
        if (!e) e = window.event;  // IE Event Model

        // Move the element to the current mouse position, adjusted as
        // necessary by the offset of the initial mouse-click.
        var newY = e.clientY - deltaY;
        if (newY < topBoundary) {
        	newY = topBoundary;
        }
        if (newY > bottomBoundary - elementHeight) {
        	newY = bottomBoundary - elementHeight;
        }
        elementToDrag.style.top = (newY) + "px";
        var ratio = scrollClient.clientHeight / (bottomBoundary);
        scrollClient.style.top = (Math.ceil(-newY * ratio)) + "px";

        // And don't let anyone else see this event.
        if (e.stopPropagation) e.stopPropagation();  // DOM Level 2
        else e.cancelBubble = true;                  // IE
    }

    /**
     * This is the handler that captures the final mouseup event that
     * occurs at the end of a drag.
     **/
    function upHandler(e) {
        if (!e) e = window.event;  // IE Event Model

        // Unregister the capturing event handlers.
        if (document.removeEventListener) {  // DOM event model
            document.removeEventListener("mouseup", upHandler, true);
            document.removeEventListener("mousemove", moveHandler, true);
        }
        else if (document.detachEvent) {  // IE 5+ Event Model
            elementToDrag.detachEvent("onlosecapture", upHandler);
            elementToDrag.detachEvent("onmouseup", upHandler);
            elementToDrag.detachEvent("onmousemove", moveHandler);
            elementToDrag.releaseCapture();
        }
        else {  // IE 4 Event Model
            // Restore the original handlers, if any
            document.onmouseup = olduphandler;
            document.onmousemove = oldmovehandler;
        }

        // And don't let the event propagate any further.
        if (e.stopPropagation) e.stopPropagation();  // DOM Level 2
        else e.cancelBubble = true;                  // IE
    }
}