By default, the ItemWidth property is -1. If the ItemWidth property is -1, the control resizes the ActiveX control to fit the control's client area. Use the ItemHeight property to specify the item's height. The property has effect only if the item contains an ActiveX control. Use the InsertControlItem property to insert ActiveX controls. Use the ItemObject property to retrieve the ActiveX object that's hosted by an item.

The ItemWidth property is interpreted like follows:

• If the ItemWidth property is greater than  zero, the ItemWidth property indicates the width in pixels of the ActiveX control. The TreeColumnIndex property indicates the column where the ActiveX control is shown. For instance, ItemWidth = 64, indicates that the width of the inside ActiveX control is 64 pixels.
• If the ItemWidth property is zero, the ActiveX control uses the full item area to display the inside ActiveX control. 
• If the ItemWidth property is -1, the TreeColumnIndex property indicates the column where the ActiveX control is shown and the inside ActiveX control is shown to the end of the control.
• If the ItemWidth property is less than -32000, the formula -(ItemWidth+32000) indicates the index of the column where the inside ActiveX is displayed. For instance, -32000 indicates that the cell in the first column displays the inside ActiveX control, -32001 indicates that the cell in the second column displays the inside ActiveX control, -32002 indicates that the cell in the third column displays the inside ActiveX control, and so on.
• If the ItemWidth property is -InnerCell or ItemCell, the ItemWidth property indicates the handle of the cell that shows the inside ActiveX. This option should be used when you need to display the ActiveX control in an inner cell. Use the SplitCell property to create inner cells, to divide a cell or to split a cell. For instance, .ItemWidth(.FirstVisibleItem) = -.InnerCell(.FirstVisibleItem, 1, 1) indicates that the inside ActiveX control is shown in the second inner cell in the second column, in the first visible item. Use the CellWidth property to specify the width of the inner cell