Extend Method [Excel 2003 VBA Language Reference]
Adds new data points to an existing series collection. Variant
expression .Extend(Source, Rowcol, CategoryLabels)
expression Required. An expression that returns a SeriesCollection object.
Source Required Variant. The new data to be added to the SeriesCollection object as a Range object.
Rowcol Optional Variant. Specifies whether the new values are in the rows or columns of the given range source. Can be one of the following XlRowCol constants: xlRows or xlColumns. If this argument is omitted, Microsoft Excel attempts to determine where the values are by the size and orientation of the selected range or by the dimensions of the array.
CategoryLabels Optional Variant. True to have the first row or column contain the name of the category labels. False to have the first row or column contain the first data point of the series. If this argument is omitted, Microsoft Excel attempts to determine the location of the category label from the contents of the first row or column.
This method is not available for PivotChart reports.
This example extends the series on Chart1 by adding the data in cells B1:B6 on Sheet1.
Charts("Chart1").SeriesCollection.Extend _ Source:=Worksheets("Sheet1").Range("B1:B6")