成都精装房新楼盘在哪:php 操作excel的问题！

代码：
<?php

//定义一个excel文件
$workbook = "C:/My Documents/test.xls";
$sheet = "Sheet1";

//生成一个com对象$ex
$ex = new COM("Excel.sheet") or Die ("连不上！！！");

//打开一个excel文件
$book = $ex->application->Workbooks->Open($workbook) or Die ("打不开！！！");

$sheets = $book->Worksheets($sheet);
$sheets->activate;

//获取一个单元格
$cell = $sheets->Cells(5,5);
$cell->activate;
//给该单元格赋值
$cell->value = 999;

//保存为另一文件newtest.xls
$ex->Application->ActiveWorkbook->SaveAs("newtest.xls");

//关掉excel，如果想看效果，则注释掉下面两行，由用户手动关掉excel
$ex->Application->ActiveWorkbook->Close("False");
unset ($ex);

?>
出现错误！
Uncaught exception 'com_exception' with message 'Error [0x80020003] 。 ' in D:\Apache Group\Apache2\htdocs\excel_test.php:8 Stack trace: #0 D:\Apache Group\Apache2\htdocs\excel_test.php(8): unknown() #1 {main} thrown in D:\Apache Group\Apache2\htdocs\excel_test.php on line 8
希望能有高手比较清楚地告诉一下是什么问题，谢谢了！