Represents major or minor gridlines on the specified chart axis. Gridlines extend the tick marks on a chart axis to make it easier to see the values associated with the data markers. This object isn't a collection. There's no object that represents a single gridline; either you have all gridlines for an axis turned on or you have them all turned off.
Using the Gridlines Object
Use the MajorGridlines property to return the GridLines object that represents the major gridlines for the axis. Use the MinorGridlines property to return the GridLines object that represents the minor gridlines for the axis. It's possible to return both major and minor gridlines at the same time.
The following example turns on major gridlines for the category axis on the chart and then formats the gridlines to be blue dashed lines.
With myChart.Axes(xlCategory) .HasMajorGridlines = True .MajorGridlines.Border.Color = RGB(0, 0, 255) .MajorGridlines.Border.LineStyle = xlDash End With