Adding/remving dynamically text boxes
$(document.createElement('div')). ...


is the same as:

$('&lt;DIV&gt;&lt;/DIV&gt;'). ....




you can just build uppon your previus jQuery statements:

$('&lt;DIV&gt;&lt;/DIV&gt;')
    .attr('id','lol')
    .html('hey hey')
    .appendTo("#div_selection_section");




$("#cornercases").change(function () {
        CORNER_CASE_LOADING();
    });


is the same as:

$("#cornercases").change(CORNER_CASE_LOADING);


and you can bind 2 events in one with jQuery so:

$("#cornercases").bind("change ready",CORNER_CASE_LOADING)




you might want to 
parsInt topvalue in the line with te var

var topvalue = parseInt($('#cornercases').val());


you will not need to repeat pareInt in each 'if' if you do that.

Also, I see that 
OLD_CASE_NUMBER is an integer (and if you do what is mesioned above), you won't need to parse that either



as far as I see the second line of your function var counter = 0; is useless, because everywhere you use counter you first set it to something else