This problem was resolved.
I had created a button in the dialog and was trying to just set it up as a CMFCButton. This means that in the Resource Editor, this appears as a 'IDC_MYCONTROL (Button Control) IButtonEditor' (as shown in the top DDL in the Properties pane). It was appearing in the RC as:
PUSHBUTTON "My Caption",IDC_MYCONTROL,7,100,54,14
What needs to happen is to delete the button from the dialog, and drag on a checkbox control from the toolbox, appearing as a 'IDC_MYCONTROL (Check-box Control) ICheckEditor' in the Properties pane. Then set the 'Appearance | Push Like' attribute to True. Within the code, this can now be set up as a CMFCButton with the corresponding BEGIN_MESSAGE_MAP entry and DoDataExchange():
DDX_Control(pDX, IDC_MYCONTROL, m_chkMFCButton);
In terms of the RC, it now appears as:
CONTROL "My Caption",IDC_MYCONTROL,"Button",BS_AUTOCHECKBOX | BS_PUSHLIKE | WS_TABSTOP,7,100,54,14
Last but not least, it is now possible to have 6 images represent the single CMFCButton if you want it to be image based:
CMFCButton::SetImage()
CMFCButton::SetCheckedImage()
where the latter function defines the appearance of the button when checked/pushed in for normal, hot, and disabled. As well, the base class CButton::SetCheck() works.
Sorry I didn't reply faster Kyudos.