It sounds like we are working on a similar task. Here's a plugin you might want to take a look at http://www.htmldrive.net/items/show/1036/JQuery-Ajax-Cool-Shopping-cart-effect
somewhere in line 44 the code puts the 'box' with corresponding text in derectly below the row of the clicked thumbnail.
$('#cart_wrapper .cart-info').append('<div class="shopp" id="each-'+thisID+'"><div class="label">'+itemname+'</div><div class="shopp-price"> $<em>'+itemprice+'</em></div><span class="shopp-quantity">1</span><img src="remove.png" class="remove" /><br class="all" /></div>');
then again somewhere in line 110 the code puts the 'box' within the defined div
$("html:not(:animated),body:not(:animated)").animate({scrollTop: targetOffset}, 800,function(){
$('#wrap #detail-'+thisID).slideDown(500);
return false;
});
go through the files and see how it all comes together, then intergrate that with your interface.