property Items.SortableItem(Item as HITEM) as Boolean
Specifies whether the item is sortable.

Item as HITEM A long expression that indicates the handle of the item being sortable.
Boolean A boolean expression that specifies whether the item is sortable.
By default, all items are sortable. A sortable item can change its position after sorting. An unsortable item keeps its position after user performs a sort operation. Thought, the position of an unsortable item can be changed using the ItemPosition property.  Use the SortableItem to specify a group item, a total item or a separator item. An unsortable item is not counted by a total field. The SortType property specifies the type of repositioning is being applied on the column when a sort operation is performed. The SortOrder property specifies whether the column is sorted ascendant or descendent. Use the SortChildren method to sort the items. Use the AllowSort property to avoid sorting a column when the user clicks the column. The ItemDivider property indicates whether the item displays a single cell, instead showing all cells. The SelectableItem property specifies whether an item can be selected.

The following screen shots shows the control when no column is sorted: ( Group 1 and Group 2 has the SortableItem property on False )

The following screen shots shows the control when the column A is being sorted: ( Group 1 and Group 2 keeps their original position after sorting )