Error handling in VC ++ to justify add to existing code

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errors

Handling

I am upgrading a code mentioned below:
what I am trying to do is I have product register for 30 and at 25th day it will remind user to register for year or two it is mentioned in code
Also I want to convert or add new code so that "Purchase Required" turn into "Available" by inserting Product code from Key code generater


Code I mentione is as follow:

// ProductCode.cpp : implementation file
//
#include "stdafx.h"
#include "Parameters.h"
#include "AddaptApp.h"
#include "ProductCode.h"
#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif
const DWORD CONFUSER = 32767;
/////////////////////////////////////////////////////////////////////////////
// CProductCodeDlg dialog
CProductCodeDlg::CProductCodeDlg(CWnd* pParent) : CDialog(CProductCodeDlg::IDD, pParent)
{
	//{{AFX_DATA_INIT(CChange)
	m_strAddapt98 = _T("Activation Required");
	m_strSA = _T("Purchase Required");
	m_strViewer = _T("Purchase Required");
	m_dwSerialNum = 0;
    m_dwProductCode = 0;
	//}}AFX_DATA_INIT
}
/////////////////////////////////////////////////////////////////////////////
// CProductCodeDlg dialog
void CProductCodeDlg::DoDataExchange(CDataExchange* pDX)
{
	CDialog::DoDataExchange(pDX);
	//{{AFX_DATA_MAP(CProductCodeDlg)
	DDX_Text(pDX, IDC_ADDAPT98, m_strAddapt98);
	DDX_Text(pDX, IDC_RTD, m_strSA);
	DDX_Text(pDX, IDC_VIEWER, m_strViewer);
	DDX_Text(pDX, IDC_PRODUCTCODE, m_dwProductCode);
	DDX_Text(pDX, IDC_SERIALNUM, m_dwSerialNum);
	//}}AFX_DATA_MAP
}
BEGIN_MESSAGE_MAP(CProductCodeDlg, CDialog)
	//{{AFX_MSG_MAP(CProductCodeDlg)
	ON_EN_CHANGE(IDC_PRODUCTCODE, OnProductCodeEntry)
	ON_BN_CLICKED(ID_DONE, OnDone)
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()
/////////////////////////////////////////////////////////////////////////////
// CProductCodeDlg message handlers
BOOL CProductCodeDlg::OnInitDialog() 
{
    CDialog::OnInitDialog();
  	CAddaptApp* pAddaptApp = (CAddaptApp*)AfxGetApp();
    m_dwSerialNum = pAddaptApp->m_dwSerialNum;
    m_dwProductCode = pAddaptApp->m_dwProductCode;
    m_dwInitialCode = m_dwProductCode;
    
    BOOL bDisableEntry = FALSE;
    if (pAddaptApp->m_bSA_Available)
        m_strSA = "Available";
    if (pAddaptApp->m_bViewer_Available)
        m_strViewer = "Available";
    if (pAddaptApp->m_bProductCodeFound)
    {
        m_strAddapt98 = "Available";
        if( pAddaptApp->m_bViewer_Available )
            bDisableEntry = TRUE;   // all options are available - good customer
    }                               // dont let anyone screw things up
	 
    else
    {
        if (m_dwProductCode == 0)
            m_strAddapt98 = "Activation Required";
        else
            m_strAddapt98 = "Product Code Invalid";
        m_strSA = "Purchase Required";
        m_strViewer = "Purchase Required";
    }
    CWnd* pWnd = GetDlgItem(IDC_PRODUCTCODE);
    if(bDisableEntry)
       pWnd->EnableWindow(FALSE);
    else
       pWnd->EnableWindow(TRUE);
	UpdateData(FALSE);
	return TRUE;
}
void CProductCodeDlg::OnProductCodeEntry()
{
   UpdateData(TRUE);
}
void CProductCodeDlg::OnOK() 
{	// update controls
	 UpdateData(TRUE);
    CAddaptApp* pApp = (CAddaptApp*)AfxGetApp();
    DWORD num = (m_dwProductCode & 0x02e0);
    
    if( (m_dwProductCode == 0x02e0 && pApp->m_bBeta) ||
        m_dwProductCode != m_dwInitialCode && 
        m_dwProductCode >= ( (m_dwSerialNum  + 1001000) & 0xfff1f) && 
        m_dwProductCode <= ( ((m_dwSerialNum  + 1001000) & 0xfff1f) + 225) )
    {
        CParameters::ProductCode(num);
        pApp->SetAvailability();
        if (pApp->m_bProductCodeFound)
           m_strAddapt98 = "Activation Required";
        if (pApp->m_bSA_Available)
           m_strSA = "Available";
        if (pApp->m_bViewer_Available)
           m_strViewer = "Available";
        UpdateData(FALSE);
    }
}
void CProductCodeDlg::OnDone() 
{
    UpdateData(TRUE);
    //CAddaptApp* pApp = (CAddaptApp*)AfxGetApp();
    DWORD num = (m_dwProductCode & 0x02e0);
    
    /*if( m_dwProductCode != m_dwInitialCode && 
        m_dwProductCode >= ( (m_dwSerialNum  + 1001000) & 0xffc1f) && 
        m_dwProductCode <= ( ((m_dwSerialNum  + 1001000) & 0xffc1f) + 0x02e0))*/
    if( (m_dwProductCode == 0x02e0 ) ||
        m_dwProductCode != m_dwInitialCode && 
        m_dwProductCode >= ( (m_dwSerialNum  + 1001000) & 0xfff1f) && 
        m_dwProductCode <= ( ((m_dwSerialNum  + 1001000) & 0xfff1f) + 225) )
    {
        CParameters::ProductCode(num);
        ((CAddaptApp*)AfxGetApp())->SetAvailability();
    }
	CDialog::OnOK();
}
void CProductCodeDlg::OnCancel() 
{
	CDialog::OnCancel();
}