expression.MinorUnit
expression Required. An expression that returns one of the objects in the Applies To list.
Remarks
Setting this property sets the MinorUnitIsAuto property to False.
Use the TickMarkSpacing property to set tick-mark spacing on the category axis.
Example
This example sets the major and minor units for the value axis.
With myChart.Axes(xlValue)
.MajorUnit = 100
.MinorUnit = 20
End With