Separator Property [Excel 2003 VBA Language Reference]
Sets or returns a Variant representing the separator used for the data labels on a chart. Read/write.
expression Required. An expression that returns one of the objects in the Applies To list.
When a value of "1" is returned, it indicates that the user has not changed the default separator which is a comma ",". You can also pass a value of "1" to change the separator back to the default separator.
The chart must first be active before you can access the data labels programmatically; otherwise a run-time error occurs.
This example sets the data label separator for the first series on the first chart to a semicolon. This example assumes a chart exists on the active worksheet.
Sub ChangeSeparator() ActiveSheet.ChartObjects(1).Chart.SeriesCollection(1) _ .DataLabels.Separator = ";" End Sub