GM_xmlhttpRequest-synchronous

GM_xmlhttpRequest({
    url : "http://www.sometime.com/?results?page=1",
    method : "GET",
    onload : function(res) {

        // some code to execute after the first GM_xmlhttpRequest finishes

        GM_xmlhttpRequest({
            url : "http://www.sometime.com/?results?page=2",
            method : "GET",
            onload : function(res) {

                // some code to execute after the second GM_xmlhttpRequest finishes

                GM_xmlhttpRequest({
                    url : "http://www.sometime.com/?results?page=3",
                    method : "GET",
                    onload : function(res) {

                        // some code to execute after the third GM_xmlhttpRequest finishes

                    }
                });

            }
        });
    }
});