How can we add a Help button to CTaskDialog?

Question

The standard AfxMessageBox allows us to include a Help button by using MB_HELP.

I can't work out how to do the same with CTaskDialog? Since, there is no official button ID for Help in the SDK:

enum _TASKDIALOG_COMMON_BUTTON_FLAGS
{
    TDCBF_OK_BUTTON            = 0x0001, // selected control return value IDOK
    TDCBF_YES_BUTTON           = 0x0002, // selected control return value IDYES
    TDCBF_NO_BUTTON            = 0x0004, // selected control return value IDNO
    TDCBF_CANCEL_BUTTON        = 0x0008, // selected control return value IDCANCEL
    TDCBF_RETRY_BUTTON         = 0x0010, // selected control return value IDRETRY
    TDCBF_CLOSE_BUTTON         = 0x0020  // selected control return value IDCLOSE
};

Yet, it does expose an OnHelp method:

The framework calls this method when the user requests help.

I assume, when they press F1.

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Note

I realise I can use AddCommandControl and get around it that way. But I would prefer a standard button just like AfxMessageBox (CodeProject tutorial: Add a Help Button to a MessageBox):