如何使用JS获取IE上传文件路径(IE7,8)

代码如下:
function validateFileSize(id, maxsize) {
            var btnsave = document.getElementById("Button2");
            btnsave.disabled = false;
            var filepath = "";
            var fileupload = document.getElementById(id);
            if (fileupload.value.length < 5) { alert('请选择文件！'); return; }
            var agent = window.navigator.userAgent;
            if (document.all) {
                var isIE7 = agent.indexOf('MSIE 7.0') != -1;
                var isIE8 = agent.indexOf('MSIE 8.0') != -1;
                //IE7和IE8获得文件路径
                if (isIE7 || isIE8) {
                    fileupload.select();
                    filepath = document.selection.createRange().text;
                }
                //IE6获得文件路径
                else
                { filepath = file.value; }
                //PageMethods.ValidateFile(filepath, maxsize, ieCallBack);
                alert(filepath);
            }
            if (agent.indexOf("Firefox") >= 1) {
                alert("FF");
                alert(getValue());
                return false;
                if (fileupload.files) {
                    var size = fileupload.files[0].fileSize;
                    if (size > parseInt(maxsize)) {
                        fileupload.parentNode.innerHTML = '<input type="file" name="' + fileupload.name + '" id="' + fileupload.id + '" onchange="disableSave(this);"/> ';
                        alert("文件超过大小！");
                    }
                    else { alert("文件上传成功！"); }
    &nb sp;           }
            }
        }

ie IE7 js