ListStore arr=new ListStore();
ComboBox cbx = new ComboBox();
cmbxNewCombobox.setDisplayField("field");
cbx.setStore(arr);
ModelData m=new BaseModelData();
m.set("field","data1");
m.set("field","data2");
combo.add(m);
//select index 1
combo.setValue(arr.getAt(1));