Do you have the file available that you could send
Ok attach it with your reply using the paperclip icon
Here you go.
Have a look at this screenshot. Hope this is what you are looking for
But you did ask for C20. No problem will set it up so you can use it for any cell. In the meantime thank you for clicking accept if that is the solution you are looking for. You can add bonus when the rest is done
Thanks! Ok here is the file with the formulas in the yellow cells
You enter the cell ref that you want to plot in cell L1 (orange cell), and the formulas and the graph will take care of the rest
Hope this is ok. Let me know if you have any questions