str.LoadString("FOO");
fooCheck.Create(str, WS_CHILD | WS_VISIBLE | WS_TABSTOP | BS_AUTOCHECKBOX, rect, this, FOO_CHECK_ID);
fooCheck.SetCheck(0);

ON_BN_CLICKED(FOO_CHECK_ID, OnFooCheckClick)

void CBeginBagWnd::OnFooCheckClick()
{
bool checked = (fooCheck.GetCheck() == BST_CHECKED);
}

ON_BN_CLICKED