Sets or returns the maximum value to be used in the category (x) axis
When creating new charts, or reading in charts where this value is not set, this property will return 0, which represents that this property does not contain a value and Excel will automatically determine an appropriate maximum for your category axis. Unfortunately, there is no way to distinguish between this state and when the MaximumValue property is actually set to zero.
This property can be set to less than the CategoryAxis.MinimumValue, although that is an illegal state. We allow this so that the order of operations does not matter when setting both the MinimumValue and MaximumValue to different values. However, if the MaximumValue is still less than the MinimumValue when you try to save, the MinimumValue will be treated as the MaximumValue and vice versa so that the resulting file is not corrupt.
These properties will only effect the axis if CategoryAxis.DisplayType is set to TimeScale.