property Group.ItemWidth as Long
Retrieves or sets the item's width. -1 if it's the group's client width.

TypeDescription
Long A long expression that indicates the item's width.

Use the ItemHeight and ItemWidth properties to specify the size for the item in the group. If the ItemWidth property is grater than zero, the control auto arranges the items in the group to fit its client area. If the ItemWidth property is less than zero only one item is displayed into a line.