Handle to window for PropertySheet

Question

The below code, creating a Property Sheet, works without problem in an Application File.

.......

CProp_Sheet Pr_Sheet(_T("PS"));

CPr_Page_1 Pr_Page_1;
CPr_Page_2 Pr_Page_2;

Pr_Sheet.AddPage(&Pr_Page_1);
Pr_Sheet.AddPage(&Pr_Page_2);

m_pMainWnd = &Pr_Sheet;

int nResponse = Pr_Sheet.DoModal();

However, when I put the same code in a DLL, and call it from a menu item in another Application, m_pMainWnd cannot be used (the menu in the Application is to remain visible behind the Property Sheet).

I have tried to create a handle

CWnd* m_pWnd = &Pr_Sheet;

and use m_pWnd in the CProp_Sheet constructor, but although compiling correctly at run time failure always occurs at

CProp_Sheet::OnInitDialog().

Thanks in advance for any comments.