Something

<div id="place1"></div>
<div id="place1"></div>

<div onClick="showUser('place1.php','place1','add')">button or whatever</div>
<div onClick="showUser('place2.php','place2','del')"> button or whatever </div>

function showUser(url,div,toggle) {
var xmlHttp;
var action;
var sendto;

xmlHttp=GetXmlHttpObject()
if (div) { sendto = div; }
if (toggle) { action = toggle; } else { action = "add"; }

var retailer=document.formname.retailer.value;
var serial=document.formname.serial.value;
var region=document.formname.regionselect.value;
var county=document.formname.countyselect.value;
var input=document.formname.input.value;

var url=url+"?retailer="+escape(retailer)+"&serial="+escape(serial)+"&region="+escape(region)+"&county="+escape(county)+"&town="+escape(input)+"&action="+escape(action);
xmlHttp.onreadystatechange=function() {
if (xmlHttp.readyState=='4' || xmlHttp.readyState=="complete") {
document.getElementById(sendto).innerHTML=xmlHttp.responseText;
}
}
xmlHttp.open("GET",url,true);
xmlHttp.send(null);
}

function GetXmlHttpObject() {
xmlHttp=null;
try {
// Firefox, Opera 8.0+, Safari
xmlHttp=new XMLHttpRequest();
}
catch (e) {
//Internet Explorer
try { xmlHttp=new ActiveXObject("Msxml2.XMLHTTP"); }
catch (e) { xmlHttp=new ActiveXObject("Microsoft.XMLHTTP"); }
}
return xmlHttp;
}