<div class="1">1</div> // 10px height
<div class="2">2</div> // 13px height
<div class="3">3</div> // 11px height
… // … height

var divTops = [];  //Start an empty array
$(document).ready(function(){  //When the DOM loads
    $('div').each(function(e){ //For each div
        var top = $(this).offset().top; //Get its top
        divTops.push(top);  //and push that top into the array
    });
});

$(window).scroll(function(){  //When the user scrolls
    var scrolled = divTops.indexOf($(window).scrollTop());  //get the index number
    if(scrolled === 0){  // Use the index number to control whatever is there.
        //Do something with the first div
    } else if(scrolled === 1){
        //Do something with the second div
    } else if(scrolled === 2){
        //Do something with the third div
    } else {

    }
});