using   System.Runtime.InteropServices;     
        
  [DllImport("User32.dll",   CharSet   =   CharSet.Auto)]     
  public   static   extern   int   GetWindowThreadProcessId(IntPtr   hwnd,   out   int   ID);     
  protected   void   Button1_Click(object   sender,   EventArgs   e)     
  {     
      Excel.ApplicationClass   excel   =   new   Microsoft.Office.Interop.Excel.ApplicationClass();     
      excel.Workbooks.Open("d:\aaa.xls",   Type.Missing,   Type.Missing,   Type.Missing,   Type.Missing,   Type.Missing,   Type.Missing,   Type.Missing,   Type.Missing,   Type.Missing,   Type.Missing,   Type.Missing,   Type.Missing,   Type.Missing,   Type.Missing);     
      IntPtr   t   =   new   IntPtr(excel.Hwnd);     
      int   k   =   0;     
      GetWindowThreadProcessId(t,   out   k);     
      System.Diagnostics.Process   p   =   System.Diagnostics.Process.GetProcessById(k);     
      p.Kill();                     
   }  

同时需要修改配置文件machine.config

<processModel   enable="true"   timeout="Infinite"   idleTimeout="Infinite"   shutdownTimeout="0:00:05"   requestLimit="Infinite"   requestQueueLimit="5000"   restartQueueLimit="10"   memoryLimit="60"   webGarden="false"   cpuMask="0xffffffff"   userName="System"   password="AutoGenerate"   logLevel="Errors"   clientConnectedCheck="0:00:05"   comAuthenticationLevel="Connect"   comImpersonationLevel="Impersonate"   responseRestartDeadlockInterval="00:09:00"   responseDeadlockInterval="00:03:00"   maxWorkerThreads="25"   maxIoThreads="25"/>   
  userName="machine"   改为   userName="System"

以上部分在Win2008中找不到 没有设置成功

通过设置用户权限，Asp.net模拟用户等方式任然无法杀掉Excel进程，最后的解决办法是写一个自动杀Excel进程的服务。

using System;
using System.Diagnostics;
using System.ServiceProcess;

namespace KillExcel
{
    public partial class KillExcel : ServiceBase
    {
        public KillExcel()
        {
            InitializeComponent();
        }

        protected override void OnStart(string[] args)
        {
            // TODO: 在此处添加代码以启动服务。
            double sleeptime =  60 * 1000; //1分钟
            System.Timers.Timer t = new System.Timers.Timer(sleeptime);//实例化Timer类，设置间隔时间为10000毫秒； 
            t.Elapsed += new System.Timers.ElapsedEventHandler(killExcel);//到达时间的时候执行事件； 
            t.AutoReset = true;//设置是执行一次（false）还是一直执行(true)； 
            t.Enabled = true;//是否执行System.Timers.Timer.Elapsed事件； 

        }
        public void killExcel(object source, System.Timers.ElapsedEventArgs e)
        {
            Process[] myProcesses;
            DateTime startTime;
            myProcesses = Process.GetProcessesByName("Excel");
            //得不到Excel进程ID，暂时只能判断进程启动时间
            foreach (Process myProcess in myProcesses)
            {
                startTime = myProcess.StartTime;

                if ((DateTime.Now-startTime).Minutes>1)
                {
                    myProcess.Kill();
                }
            }
        }

        protected override void OnStop()
        {
        }
    }
}

 上边的服务出现不稳定问题，运行一段时间以后就会，自动杀死Excel进程，不再计算Excel启动时间与当前时间是否符合设定的时间差，还没找到原因。

计时器不能稳定运行，最后使用了线程方式来定时，这次可以稳定的运行了

public partial class KillExcel : ServiceBase
    {
        private int _timeOut;
        private Thread _t;
        public KillExcel()
        {
            InitializeComponent();
            int to;
            int.TryParse(ConfigurationManager.AppSettings["TimeOut"], out to);
            _timeOut = to > 0 ? to : 3;
        }

        protected override void OnStart(string[] args)
        {
            // TODO: 在此处添加代码以启动服务。
            _t = new Thread(new ThreadStart(Monitor));
            _t.IsBackground = true;
            _t.Start();
        }

        private void Monitor()
        {
            int sleeptime = 60 * 1000 * _timeOut;
            while (true)
            {
                Thread.Sleep(sleeptime);
                killExcel();
            }
        }

        public void killExcel()
        {
            Process[] myProcesses = Process.GetProcessesByName("Excel");
            //得不到Excel进程ID，暂时只能判断进程启动时间
            foreach (Process myProcess in myProcesses)
            {
                if ((DateTime.Now - myProcess.StartTime).Minutes > _timeOut)
                {
                    myProcess.Kill();
                }
            }
            GC.Collect();
        }

        protected override void OnStop()
        {
            
        }
    }