if(typeof(Sys) != 'undefined')
{
    Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(QuotedDynamic_BeginRequestHandler);
    Sys.WebForms.PageRequestManager.getInstance().add_endRequest(QuotedDynamic_EndRequestHandler); 
}

var requestsInProcess = 0;

function QuotedDynamic_BeginRequestHandler(sender, args)
{
    requestsInProcess = requestsInProcess + 1;
    $(".cascading_select_button").hide();
    $(".cascading_select_button_disabled").show();

}

function QuotedDynamic_EndRequestHandler(sender, args)
{
    requestsInProcess = requestsInProcess - 1;
    if (requestsInProcess == 0)
    {
        $(".cascading_select_button").show();
        $(".cascading_select_button_disabled").hide();
    }

}