//fired when the update starts
var asyncObject;
function InitializeRequest(sender, args) { 
    if(asyncObject != null){
        if(sender._postBackSettings.sourceElement.id == asyncObject.id){
            $get(args._postBackElement.id).disabled = true;            
        }
    }
    else{
            $get(args._postBackElement.id).disabled = true;
    }
}

//fired when the update ends
function EndRequest(sender, args) {    
    if(asyncObject != null){ 
        if(sender._postBackSettings.sourceElement.id == asyncObject.id){
            $get(sender._postBackSettings.sourceElement.id).disabled = false;
        }
    }
    else{
        $get(sender._postBackSettings.sourceElement.id).disabled = false;
    }
}
        
function init(obj){    
    asyncObject = obj;
    var prm = Sys.WebForms.PageRequestManager.getInstance(); 
    prm.add_initializeRequest(InitializeRequest);
    prm.add_endRequest(EndRequest);
}