jQuery scroll to using the scroll wheel

Question

So I'm attempting to grasp the beginning of how to get a function working beyond just seeing plugins do what I ask. For example this plugin does a "jump to" upon clicking those div links in the nav. What I'd like is when you get to a certain part of a div it jumps to the rest of the div. Thereby cutting out the nav bar entirely but utilizing the easing to reach the rest of the article/photo, etc.

Currently I'm using a script for parallax by Richard Shepard and I'd like to expand the script to use the backgroundPosition: coordinates to trigger a scroll to event.

I've pasted in his code for convenience.

P.S. All this code is working as it "should" yet, it is lacking an easing between divs, and currently I have on my install jquery.easing .

P.P.S. Yet, I'm not sure where I need to start. So, I figured start with the functions that are getting the users location on the page already.

// On your marks, get set...
$(document).ready(function(){
console.log("loaded parallax");

// Cache the Window object
$window = $(window);

// Cache the Y offset and the speed of each sprite
$('[data-type]').each(function() {
    $(this).data('offsetY', parseInt($(this).attr('data-offsetY')));
    $(this).data('Xposition', $(this).attr('data-Xposition'));
    $(this).data('speed', $(this).attr('data-speed'));
});

// For each element that has a data-type attribute
$('section[data-type="background"]').each(function(){

    // Store some variables based on where we are
    var $self = $(this),
        offsetCoords = $self.offset(),
        topOffset = offsetCoords.top;

    // When the window is scrolled...
    $(window).scroll(function() {

        // If this section is in view
        if ( ($window.scrollTop() + $window.height()) > (topOffset) &&
             ( (topOffset + $self.height()) > $window.scrollTop() ) ) {
            // console.log("scrolling background");

            // Scroll the background at var speed
            // the yPos is a negative value because we're scrolling it UP!
            var yPos = -($window.scrollTop() / $self.data('speed'));

            // If this element has a Y offset then add it on
            if ($self.data('offsetY')) {
                yPos += $self.data('offsetY');
            }

            // Put together our final background position
            var coords = '50% '+ yPos + 'px';

            // Move the background
            $self.css({ backgroundPosition: coords });

            // Check for other sprites in this section
            $('[data-type="sprite"]', $self).each(function() {

                // Cache the sprite
                var $sprite = $(this);

                // Use the same calculation to work out how far to scroll the sprite
                var yPos = -($window.scrollTop() / $sprite.data('speed'));
                var coords = $sprite.data('Xposition') + ' ' + (yPos + $sprite.data('offsetY')) + 'px';

                $sprite.css({ backgroundPosition: coords });

            }); // sprites

        }; // in view

    }); // window scroll

}); // each data-type

}); // document ready

here is the beginning of my code within the // If this section is in view section:

                var windowheight = jQuery(window).height();
                // console.log(yPos);

                if (Math.abs(yPos) > windowheight/2) {
                    console.log("scrollto");
                    jQuery('#fourth').ScrollTo();
                }