property InsideZoomFormat.GridLineStyle as GridLinesStyleEnum
specifies the style for the vertical gridlines when a time scale unit is being zoomed.

TypeDescription
GridLinesStyleEnum A GridLinesStyleEnum expression that specifies the style to show the chart's vertical gridlines.
By default, the GridLineStyle property is exGridLinesDot4. The GridLineStyle property indicates the style of vertical gridlines being shown in the inside time-unit. The GridLineStyle property has effect only DrawGridLines property is True. The GridLineColor property specifies the color for grid lines being shown in the chart area for specified unit. The BackColorChart property specifies the unit's background color being shown in the chart ( not in the header ). The BackColor property controls the background of the time scale unit being shown in the chart's header.