Proxy Pattern

    ExecuteOrDelayUntilScriptLoaded(function () {
        (function () {
            var old_UploadFinishFunc = window.UploadFinishFunc;

            window.UploadFinishFunc = function (b, a) {
        // DO SOME WORK HERE
                return old_UploadFinishFunc.apply(this, arguments);
            }
        })();
    }, "dragdrop.js");