You can turn on ajax mode of KoolCalendar by setting AjaxEnabled to true. Also you may set the loading image with $AjaxLoadingImage property.
*Note: The KoolAjax is required.
<?php
require $KoolControlsFolder."/KoolCalendar/koolcalendar.php";
require $KoolControlsFolder."/KoolAjax/koolajax.php";
$koolajax->scriptFolder = $KoolControlsFolder."/KoolAjax";
$cal = new KoolCalendar("cal"); //Create calendar object
$cal->scriptFolder = $KoolControlsFolder."/KoolCalendar";//Set scriptFolder
$cal->styleFolder="default";
//Enable Ajax
$cal->AjaxEnabled = true;
$cal->AjaxLoadingImage = $KoolControlsFolder."/KoolAjax/loading/2.gif";
//Init calendar before render
$cal->Init();
?>
<form id="form1" method="post">
<div style="padding-top:20px;padding-bottom:40px;width:650px;<?php if ($style_select=="black") echo "background:#333"; ?>">
<?php echo $koolajax->Render();?>
<?php echo $cal->Render();?>
</div>
</form>
KoolCalendar - Advanced PHP CalendarFullVersion 1.9.0.0 released on 04/16/2012