How to get values without page Upload

hii as i see some code in which we can sent data on the run time when we enter something in input & go for next that post that data into action forum which we define in Ajax action
that is for the checking for username field on run time wihtout loading the page
here is code

<SCRIPT type="text/javascript">
<!--

pic1 = new Image(16, 16); 
pic1.src = "images/loader.gif";

$(document).ready(function(){

$("#username").change(function() { 

var usr = $("#username").val();

if(usr.length >= 4)
{
$("#status").html('<img src="images/loader.gif" align="absmiddle">&nbsp;Checking availability...');

    $.ajax({  
    type: "POST",  
    url: "userchk.php",  
    data: "username="+ usr,  
    success: function(msg){  
   
   $("#status").ajaxComplete(function(event, request, settings){ 

	if(msg == 'OK')
	{ 
        $("#username").removeClass('object_error'); // if necessary
		$("#username").addClass("object_ok");
		$(this).html('&nbsp;<img src="images/tick.gif" align="absmiddle">');
	}  
	else  
	{  
		$("#username").removeClass('object_ok'); // if necessary
		$("#username").addClass("object_error");
		$(this).html(msg);
	}  
   
   });

 } 
   
  }); 

}
else
	{
	$("#status").html('<font color="red"> username have at least <strong>4</strong> characters.</font>');
	$("#username").removeClass('object_ok'); // if necessary
	$("#username").addClass("object_error");
	}

});

});

//-->
</SCRIPT>

and here we give id in forum input field

<input id=“username” name=“username” type=“text” value=“”/>

Simple i want that i can get values of more input field at the same time when user enter data in those

how i’ll get that

mean i can get the values of multiple when we enter values at run time