read failed: sharing violation

Dear Experts,

I am writing a program to backup some in used file. No matter I used
"shareDenyWrite"/"shareDenyRead"/"shareDenyNone", the using file can't be
copy.

(if using native copy, it will prompt "sharing violation" error).

How can I read/backup such files with vc? (no need to care integrity, just
want to capture a snap.

Million thanks.

-AL

=====Attached what I programmed for your reference.
#include <afx.h>
#include <afxwin.h>
#include <iostream>

using namespace std;

CWinApp theApp;

int main(int argc, char *argv[])
{
   if (!AfxWinInit(GetModuleHandle(NULL), NULL, GetCommandLine(), 0))
   {
      cout << "panic: MFC couldn't initialize!" << endl;
      return 1;
   }

   // constructing these file objects doesn't open them

   CFile sourceFile;
   CFile destFile;

   // see that we have a reasonable number of arguments

   if (argc != 3)
   {
      cout << "usage: " << argv[0];
      cout << " <source> <dest>" << endl;
      cout << endl;
      return 1;
   }

 // we'll use a CFileException object to get error information

   CFileException ex;

   // open the source file for reading

   if (!sourceFile.Open(argv[1],
      CFile::modeRead | CFile::shareDenyWrite, &ex))
   {
      // complain if an error happened
      // no need to delete the ex object

      TCHAR szError[1024];
      ex.GetErrorMessage(szError, 1024);
      cout << "Couldn't open source file: ";
      cout << szError;
      return 1;
   }
   else
   {
      if (!destFile.Open(argv[2], CFile::modeWrite |
            CFile::shareExclusive | CFile::modeCreate, &ex))
      {
         TCHAR szError[1024];
         ex.GetErrorMessage(szError, 1024);
         cout << "Couldn't open source file: ";
         cout << szError;

         sourceFile.Close();
         return 1;
      }

      BYTE buffer[4096];
      DWORD dwRead;

      // Read in 4096-byte blocks,
      // remember how many bytes were actually read,
      // and try to write that many out. This loop ends
      // when there are no more bytes to read.

      do
      {
         dwRead = sourceFile.Read(buffer, 4096);
         destFile.Write(buffer, dwRead);
      }
      while (dwRead > 0);

      // Close both files

      destFile.Close();
      sourceFile.Close();
   }

   return 0;
}