dynamic number of points to plot in chart

I am using the following formulas for X and Y Values

X value

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Y value

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For the X value, I want to give the choice as to the number of points to plot on the chart. The current formula for the X value is set to plot 10 points of data. How can I link that part of the code to a cell (cell E19 for example)?

Thanks for any comments.

I have attached sample spreadsheet if needed.

I'm not exactly sure as to what you are looking for but here is a sample that I made fo a friend of mine in Memphis. He took it apart and used several Ideas out of this dashboard.