Please state your budget for providing this 'little example'.  

Alternately, you might actually demonstrate some effort
at figuring what polilop was saying, with appropriate use
of your favorite search engine, to *avoid* asking stupid
questions.

you will need to learn about AJAX before.
looka at http://www.w3schools.com/ajax/default.asp
or at:
http://www.ajaxtutorial.net/index.php/2006/03/08/simple-ajax-functions-snippets/
Allso look at ajax prototype, might be helpful

here is  what i use for simple ajax requests (found it on the web but was
unable to find the page again):
ajaxUpdate( 'display', '/myUpdate.do',
{params:'value='+document.getElementById('myValue').value,async:false,startfunc:'loadingMessage();'
});

elemid=id of element that will receive the return information
url =url of the servlet that will make the update eg. myServletUpdate
options = you put options in{} like this, startfunc is if you need to run a
function before the ajax call.

function ajaxUpdate( elemid, url, options )

{

var params = options.params || "";

var meth = options.meth || "post";

var async = options.mode || true;

var startfunc = options.startfunc || "";

var endfunc = options.endfunc || "";

var errorfunc = options.errorfunc || "";

var req = false;

params = params+"&random="+Math.round(10000*Math.random());

//Enkoding for utf-8 do not use if page allready in utf-8

params=encodeURI(params)

//alert(params);

try {

req = new XMLHttpRequest();

} catch(e1) {

try {

req= new ActiveXObject("Microsoft.XMLHTTP");

} catch(e2) {

try {

req = new ActiveXObject("Msxml2.XMLHTTP");

} catch(e3) {

return false;

}

}

}

if( startfunc != "" )

eval( startfunc );

req.open( meth, url+( params != "" ? "?"+params : "" ), async );

req.setRequestHeader( "Content-Type",
"application/x-www-form-urlencoded;charset=UTF-8" );

req.onreadystatechange =

function()

{

if ( req.readyState == 4 )

{

if ( req.status == 200 )

{

hideMessage();

document.getElementById(elemid).innerHTML = req.responseText;

if( endfunc != "" )

eval( endfunc );

return true;

}

else

{

hideMessage();

if( endfunc != "" )

eval( endfunc );

if( errorfunc != "" )

eval( errorfunc );

return false;

}

}

};

req.send(null);

}

Hope this helps.