SeriesLines Property [Excel 2003 VBA Language Reference]
Returns a SeriesLines object that represents the series lines for a 2-D stacked bar, 2-D stacked column, pie of pie, or bar of pie chart. Read-only.
This example turns on series lines for chart group one in Chart1 and then sets their line style, weight, and color. The example should be run on a 2-D stacked column chart that has two or more series.
With Charts("Chart1").ChartGroups(1) .HasSeriesLines = True With .SeriesLines.Border .LineStyle = xlThin .Weight = xlMedium .ColorIndex = 3 End With End With