Associating dialog box with a database called from a menu item for display

I am working on a database application using CRecordSet. Instead of using the normal way of display I have created a menu called database & a item called Display which calls a dialog box. In the initdialog function I have used the following commands:
m_pSet->MoveFirst();
m_pSet->m_Acc_No = dlg.m_Acc_No;
:
:
UpdateData(FALSE);
But I am getting a runtime Exception on the first command. I have used a forward dlgdbSet class declaration in my dialog's header file & m_pSet is a member of dialog class.
How can I solve this problem using VC 5.0.