You should show/hide the div using client-side scripting, else you need to perform a postback to the server and reload (at least part of) the page.
option 1:
You can add an onclick (I believe) handler that calls a client-side function.
I ussually do something like this:
function on_checkbox_clicked(checkboxid, divid){
if(document.getElementById(divid).style.visibility == "hidden"){
document.getElementById(divid).style.visibility = "visible";
}
else{
document.getElementById(divid).style.visibility = "hidden";
}
}
it will be a little more complex than that, but you get the idea. positioning the div tags is done through html and css.
option 2:
Have a look here:
JQuery UI[
^] which gives very nice results fast, but is a bit more complex.
hope this gets you along the way.