TickMarkSpacing Property
Returns or sets the number of categories between tick marks on the specified axis. Applies only to category axes. Use the MajorUnit and MinorUnit properties to set tick-mark spacing on value axes. Read/write Long.
expression.TickMarkSpacing
expression Required. An expression that returns a ChAxis object.
Example
This example sets the number of categories between tick marks on the specified axis to two.
ChartSpace1.Charts(0).Axes(1).TickMarkSpacing = 2