property Items.CellCaption([Item as Variant], [ColIndex as Variant]) as Variant

Retrieves or sets the text displayed on a specific cell.

Item as Variant A long expression that indicates the item's handle.
ColIndex as Variant A long expression that indicates the column's index, or the handle to the cell, if the Item parameter is 0, a string expression that indicates the column's caption or the column's key.
Variant A variant expression that indicates the cell's caption. The cell's caption supports built-in HTML format.

The CellCaption property specifies the cell's caption. To associate an user data for a cell you can use CellData property. Use the CellCaptionFormat property to use HTML tags in the cell's caption.  Use the ItemData property to associate an extra data to an item. To hide a column you have to use Visible property of the Column object. The AddItem method specifies also the caption for the first cell in the item. Use the SplitCell property to split a cell. The CellCaption property indicates the formula being used to compute the field, if the CellCaptionFormat property is exComputedField. The ComputedField property specifies the formula to compute the entire column. Use the ConditionalFormats method to apply formats to a cell or range of cells, and have that formatting change depending on the value of the cell or the value of a formula.

Note: A cell is the intersection of an item with a column. All properties that has an Item and a ColIndex parameters are referring to a cell. The Item parameter represents the handle of an item, and the ColIndex parameter indicates an index ( a numerical value, see Column.Index property ) of a column , the column's caption ( a string value, see Column.Caption property ), or a handle to a cell ( see ItemCell property ). Here's few hints how to use properties with Item and ColIndex parameters:

Gantt1.Items.CellBold(, Gantt1.Items.ItemCell(Gantt1.Items(0), 0)) = True
Gantt1.Items.CellBold(Gantt1.Items(0), 0) = True
Gantt1.Items.CellBold(Gantt1.Items(0), "ColumnName") = True