C / C++ / MFC

CMainDialog::SomeFunction()
{
    CSubDialog    Dlg(this);
    Dlg.DoModal();
    ...
    CSubDialog    *pDlg1;
    pDlg1 = new CDialog(this);
    pDlg1->Create(IDD_SOMEID);
    ...
    CSubDialog    *pDlg2;
    pDlg2 = new CDialog;
    pDlg2->Create(IDD_SOMEID, this);
}

class MainFormDialog : public CDialog
{
    public:
        int m_nSomeNumber;
};
 
BOOL CRemoveFilterDlg::OnInitDialog()
{
    MainFormDialog *pParent = GetParent();
    pParent->m_nSomeNumber = 1234;
}

class CRemoveFilterDlg : public CDialog
{
    public:
        int m_nYear;
};
 
void CRemoveFilterDlg::OnOK()
{
    dlg2.m_nYear = 2004;
    return CDialog::OnOK();
}
 
void MainFormDialog::Om_clickmenu()
{
    CRemoveFilterDlg dlg2;
    dlg2.DoModal();
    // access dlg2.m_nYear here
}