Please try to process:
comboBox.EnableWindow(true);
before:
m_wndToolBar.ReplaceButton(ID_REPORT_SELECT_COMBO, comboBox, TRUE);
then provide a command reaction for your parent frame:
BEGIN_MESSAGE_MAP(CYourFrame, CFrameWndEx)
ON_COMMAND(ID_CBBOX_CONN_PORT, &CYourFrame::OnClickReportCB)
END_MESSAGE_MAP()
void CYourFrame::OnClickReportCB()
{
}
It should make the box enabled :)