SetScheduleVerticalLines is not changing the grid lines (for programmers)

Question:     

I'm using the automation interface to build a schedule based on a template.  However, I'm trying to set/control some of the properties of the chart.  Most of it is working just fine, but for some reason I'm not able to correctly set the Gantt Chart vertical grid line properties correctly.  Initially I create the Milestones object:

        Dim oM = CreateObject("Milestones")

        oM.Activate()

        oM.Use20Columns()

        oM.AutoSizeRows(1)

        oM.AllColorsAreRGB()

Later on, as I'm setting properties of the chart, I want to set the vertical grid lines to calendar year, red and dotted:

        oM.SetScheduleVerticalGridlines(0, CStr(RGB(255, 0, 0)), 1, 1)

However, the grid lines remain fiscal year, black and solid, and this is before I've added any task rows at all.  Am I calling it incorrectly or something?