Change calculated field based on filter

Hey All,

I have a graph that looks like this :

I am sorting the rows based on the slope of the trend line, which is in a calculated field called "slope".

However, when I filter out some of the data, the graph changes, and so does the slope of the trendline :

Is there any way to change the value of the calculated field (which would then change the sort order) based on the value of the filter?

The workbook is attached. The worksheet in interest is called "Points over Time"

Thanks,

Jay