1:
2:
3:
4:
5:
6:
7:
8:
9:

var hMainForm, hCombobox : HWND;
    buffer   : String;

hMainForm := CreateDialog(hInstance, 'MAIN_FORM', 0, @dlgfunc);

hCombobox := GetDlgItem(hMainForm, IDC_ComboBox);

buffer := 'Peter';
SendMessage(hComboBox, CB_ADDSTRING, 0, Integer(@buffer));