Is it possible to draw lines on a graph/chart using given starting points?

We make results for different subjects at university. We're required to draw lines at starting points of each grade and average in Graphs/Charts. Suppose average is 57.25, I'd have to draw a line at that point. Similarly I'd have to draw lines for starting points of grades say 81, 77, 66, 53, 42 viceversa. I was wondering if there is a way to automatically draw these lines in Graphs/Charts based on ranges/values. It'd save me a lot of time. Its a headache to draw lines again over again till results get approved. I'm attaching a sample sheet for view. Any help in this regard will be highly appreciated.

gujjar, please take the time to read our forum rules with regards your title, changing your title will get you the help that you need, try to be more descriptive of the problem i.e Is it possible to draw lines on a graph/chart using given starting points?

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You can create those lines using extra series and X error bars.
The grade labels are based on yet more data series.

And you can do the same for the percentage boundaries if you want them as well.

Once you have added the addition series in order to apply the error bars you would

Double click the series, to display Format dialog
On the X Error Bars tab select Both directions and set the percentage value to 100.

You can then format the error bars as required, no cap and dotted line.