Increases the label box size for an X category label (Z and Y category labels are unaffected) in a Chart. It is only active when the ShowLabel (Property)is enabled and the AutoFrequency (Property) is disabled. It is unavailable for Pie Charts. This property is used primarily for sequential labels, for example, time, day or number labels. For regular name-based labels, this property should be disabled so that the user can view each label name.
This example shows how to enable the ExpandLabelBox property:
ActiveDocument.Sections["Chart"].LabelsAxis.XAxis.ExpandLabelBox=true