So I have a MultiSelect box with x values which I need the ability to move to another MultiSelect box and vise versa.
I had same problem but i found out a way around it
    
    
jquery
$('#select1').click(function () {
     return !$('#select1 option:selected').remove().appendTo('#select2');
});
$('#select2').click(function () {
     return !$('#select2 option:selected').remove().appendTo('#select1');
 });
if want a button add a add >> and jquery click selector here
example http://jsfiddle.net/diffintact/GJJQw/3/