Only used when ChartAxis.AnnoFormat property is NumericManual or DateManual. The AnnoFormatString property specifies a custom string for formatting the annotations along the axis.
When the AnnoFormat property is NumericManual, the AnnoFormatString property can be set to format strings as described by the .Net double.ToString(AnnoFormatString) method call. Custom numeric format strings are described in detail by the .Net documentation under "Custom Numeric Format Strings". If the AnnoFormatString property is empty, then "g" or General is used.
When the AnnoFormat property is DateManual, the AnnoFormatString property can be set to format string as described by the .Net DateTime.ToString(AnnoFormatSTring) method call. Custom DateTime format strings are described in detail by the .Net documentation under "Date and Time Format Strings". If the AnnoFormatString property is empty, then ChartField selects a format string appropriate for the time span defined by the axis maximum and minimum values.
