function CallMe(src, dest) 
{ 
var ctrl = document.getElementById(src); 
// call server side method 
PageMethods.GetUserName(ctrl.value, CallSuccess, CallFailed, dest); 
} 
// set the destination textbox value with the UserName 
function CallSuccess(res, destCtrl) 
{ 
var dest = document.getElementById(destCtrl); 
dest.value = res; 
} 
// alert message on some failure 
function CallFailed(res, destCtrl) 
{ 
alert(res.get_message());
}