create a line in a chart

[ioncila]

Hi
Charts are very hard for me. Here's a thing that I woukd wish to do:

Is there a way via general or vba to create a vertical line in a line chart that could show the moment when data stay constant?
I dont know if I´m explaining the issue correctly.
If you please, see the attached file.

Thank you very much.
Ioncila

[Andy Pope]

You can use a dummy series on the secondary axis with only 1 displayed data point.
Add 100% minus Y error bar to draw the vertical line.

I did not know whether the constant point was manually defined or to be determined by formula.

I used formula to determine duplicate columns of data. Another to determine 3 consecutive repeats. And a final formula, used to plot the series, which identifies the first point of constant data.

To do it manually simply put a 1 in the month that should be marked with the vertical line.