var items2 = ["a", "ab", "abc", "apple", "boy", "cat", "dog"];
var editableComboBoxCellType = new GC.Spread.Sheets.CellTypes.ComboBox().items(items2).editable(true);
editableComboBoxCellType.itemHeight(50);
activeSheet.getCell(1, 3).cellType(editableComboBoxCellType);