jQuery.expr[':'].aspnet = function(elem, i, match) { return $(elem).filter('[id$=' + match[3] + ']').length == 1; }

var ddlReasons = $("select:aspnet('ddlReasons')")[0];
var DELIVERY_TIME_GUID = '156e6cef-6e46-426f-9582-21a593e54313';

$(ddlReasons).change(function() {
    var currentVal = $(ddlReasons).val();
    if (currentVal == DELIVERY_TIME_GUID)
        $("#jqsTipBoxCon").slideDown(500);
    else
        $("#jqsTipBoxCon").slideUp(500);
});