[CONNECT C++] Combo Box: remove unwanted items

Here's my Combo Box resource definition...

DItem_ComboBoxRsc COMBOBOXID_AreaAltFormatChoice =
    {
    NOCMD, LCMD, NOSYNONYM, NOHELP, MHELPTOPIC,
    HOOK_CBO_AreaAltFormatChoice, NOARG,
    46, "", "", "", "", NOMASK,
    0, 12, 4, 0, 0,
    COMBOATTR_READONLY | COMBOATTR_DISPLAYALLCOLUMNS | COMBOATTR_USEMODELVALUE |
    COMBOATTR_FONTBYCOLUMN | COMBOATTR_FULLWIDTH,"","g_vars.nAltAreaFormatChoice",
        {
        {18*XC,  46, ALIGN_LEFT, "dummy"},
        }
    }

It has a single row defined, labelled 'dummy'.  If I remove that row from the resource, the dialog fails to load.

The hook function assigns a ListModel to that ComboBox.  That works fine.  However, the dummy row remains...

There's no function that I can see to clean out a ComboBox prior to assigning a ListModel.  How do I get rid of dummy?