[jQuery] ajax form post help needed

[Info]

I am using the ajax form plugin....working GREAT however I need to add
a loading grapic to display while it does the post. I have a div
(loader) thats just waiting to turn on and off but I can't get it to
show...any help would be great!!

code:

$(document).ready(function(){
                        $('#chk_area').ajaxForm(function(service_return) {
                                if (jQuery.trim(service_return)==1){
                                         alert("Thank you for your comment! - 
1");
                                }
                                else if (jQuery.trim(service_return)==0){
                                        alert("Thank you for your comment! - 
0");
                                }
                        });
                });