how to append log details in log file in MFC (VC++)?

i have created one method to write to Log file but each time it overrite the log details , i want to create a new entry everytime for logging details.My log method is as below :

void CNDSConnectDlg::WriteLogData()
{


    CString strUserName = "";
    m_editUserName.GetWindowText(strUserName);
    FILE * pFile = NULL;        
    int iErr = 0;
    iErr = fopen_s(&pFile,"NDSLog.txt","w");

    if (iErr == 0)
    {

    CString strConnectionStatus = "";
    CString strServerAddress = "";
    CString strDateTime = "";
    SYSTEMTIME systime;
    GetLocalTime(&systime); 


    if(m_bConnectionStaus == true)
    {
       strConnectionStatus = "Success";
    }
    else
    {
       strConnectionStatus = "Failure";
    }

    strUserName.Format("%s",strUserName);
    strConnectionStatus.Format("%s",strConnectionStatus); 
    strServerAddress.Format("%s",m_strIPAddress);
    strDateTime.Format("%i:%i:%i\\%02i-%02i-%02i",
            systime.wHour,
            systime.wMinute,
            systime.wSecond,
            systime.wYear,
            systime.wMonth,
            systime.wDay);

    fputs("UserName = " + strUserName + " connected to "
          "ServerAddress = " +strServerAddress + " at "
          "Date/Time = " + strDateTime + " "  
          "ConnectionStatus = " +strConnectionStatus + " ",pFile); 


    fclose (pFile); 
    }
    else
    {
         MessageBox("Error in writing to Log","NDS",MB_ICONERROR | MB_OK);

    开发者_C百科}

}

Any help is highly appreciated . Thanks in Advance.

Open file with "a" (append) instead of "w".

Open file with a+ instead of a.