Stopping fixed position scrolling at a certain point? ~ Reverse

Question

In this StackOverflow question: Stopping fixed position scrolling at a certain point? you can find jQuery for stopping an element thats going top to bottom and stopping said element on its way to the bottom somewhere in the middle of the page.

I don't have much experience with jQuery and was hoping the following code could be reversed to do the same if it was scrolling bottom to top and stopping halfway.

Thanks!

var windw = this;

$.fn.followTo = function ( pos ) {
    var $this = this,
        $window = $(windw);
    
    $window.scroll(function(e){
        if ($window.scrollTop() > pos) {
            $this.css({
                position: 'absolute',
                top: pos
            });
        } else {
            $this.css({
                position: 'fixed',
                top: 0
            });
        }
    });
};

$('#f').followTo(250);

#f {
    background:#ace;
    padding:20px;
    width:200px;
    position:fixed; top:0; left:0;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.0/jquery.min.js"></script>
<div id="f">
    I'm going to follow you only so far...
</div>
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