Focus does not change when tab key is pressed in nested CWnd-Derived class

Environment: VS2013, MFC, C ++

I have a dialog generated with CDialog with 2 static buttons (OK, Cancel), created with the dialog editor. In addition, the dialog should contain a dynamically created instance of the CWnd-Derived class, which contains 2 edit fields.

The problem is that I cannot move focus with the tab key between edit boxes, and I also cannot get one of the boxes to have the original focus when the dialog is opened. When I press the tab key, the first edit box becomes focused, but from that point I cannot move the focus with the tab key (mouse clicking works).

I already created a CWnd with WS_EX_CONTROLPARENT style but it still doesn't work to move focus. So where is the problem? What I have done so far:

//the CDialog-class which should be the container for the CWnd
//.h
class CDlgSelCatalogItem : public CDialog {
   CListFilterInput _ctrlList; //CWnd-Derived, contains 2 Edit-Boxes
}

//.cpp
BOOL CDlgSelCatalogItem::OnInitDialog()
{
   CRect rectList(10, 10, 100, 50);
   _ctrlList.Create(rectList, this);
}

//the CWnd-derived class that contains 2 edit-boxes
//.h
class CListFilterInput : public CWnd {
   BOOL Create(const RECT& rect, CWnd* pParentWnd);

   //2 Edit-Boxes   
   CEdit _ctrl1;
   CEdit _ctrl2;
}

BOOL CListFilterInput::Create(const RECT &rect, CWnd *pParentWnd)
{
   BOOL bRetVal;

   bRetVal = CWnd::CreateEx(WS_EX_CONTROLPARENT, NULL, _T(""), WS_CHILDWINDOW | WS_VISIBLE,
      rect, pParentWnd, CTRL_ID_THIS);

   if (bRetVal == TRUE){
    //1st box
    CRect rectTextbox = ...; //calculate rect fox box

    bRetVal = _ctrl1.Create(
        WS_CHILDWINDOW | WS_VISIBLE | WS_TABSTOP | ES_LEFT | ES_AUTOHSCROLL,
        rectTextbox, this, CTRL_ID_TEXTBOX);

    //2nd box above 1st
    rectTextbox.MoveToY(rectTextbox.top - rectTextbox.Height());
    bRetVal = _ctrl1.Create(
        WS_CHILDWINDOW | WS_VISIBLE | WS_TABSTOP | ES_LEFT | ES_AUTOHSCROLL,
        rectTextbox, this, CTRL_ID_TEXTBOX+1);

      //set input-focus initially on 1st textbox - doesnt work
      _ctrl1.SetFocus();
   }

   return bRetVal;
}