Represents a unit label on an axis in the specified chart. Unit labels are useful for charting large values—for example, in the millions or billions. You can make the chart more readable by using a single unit label instead of large numbers at each tick mark.
Using the DisplayUnitLabel Object
Use the DisplayUnitLabel property to return the DisplayUnitLabel object. The following example sets the display label caption to "Millions" on the value axis in Chart1, and then it turns off automatic font scaling.
With Charts("Chart1").Axes(xlValue).DisplayUnitLabel
.Caption = "Millions"
.AutoScaleFont = False
End With