Disable the menu/action on the header of ListGrid

[wing.t.lee]

I use SmartGWT 3.0 Power Edition and I use ListGrid component to show the data. I want to know how can I disable the menu that I click in the arrow on the column of ListGrid header? I want to know whether I can disable the whole menu and how to disable particular action on the menu?

final ListGrid listGrid = new ListGrid("Item Supply", false, null);

listGrid.setDataSource(ItemSupplyXmlDS.getInstance());
final ListGridField itemIdField = new ListGridField("itemID");   
final ListGridField itemNameField = new ListGridField("itemName");
final ListGridField skuField = new ListGridField("SKU");   
final ListGridField descriptionField = new ListGridField("description");   
final ListGridField categoryField = new ListGridField("category");   
final ListGridField unitsField = new ListGridField("units");  
unitsField.setPrompt("<b>Units Value : </b><br>Roll, Ea, Pkt, Set, Tube, Pad, Ream, Tin, Bag, Ctn, Box");
final ListGridField unitCostField = new ListGridField("unitCost");   
final ListGridField inStockField = new ListGridField("inStock");   
final ListGridField nextShipmentField = new ListGridField("nextShipment");   


listGrid.setFields(itemIdField, itemNameField, skuField, descriptionField, categoryField, unitsField, unitCostField, inStockField, nextShipmentField);   

listGrid.fetchData();