Its proably trivially simple just I've never done it.
I have searched farily extensively in your archives and cant find an example. I know or rather I very strongly suspect this is not difficult.

I want to creat a Chart that automatically selects the last 30/31 data sets from an acculating spreadsheet.

I.e. If If I add a new row of data set to the spreadsheet the chart will automatically drop the oldest/earliest data set and include the latest data set in what I'm seeing instead.

My aim is to have the last approximately 30 days worth of data from constantly a accumlating data set, displayed along with key metrics I calculate from the data generateddata.

To give a more concrete example.
If was logging the 4 hourly average temperatures of a storage tank I would want the Chart I see today to show the recorded values along with the calculated energy use etc from 12th Sep to 12th.

The chart I will see tomorrow would show from the 13th Sep to 13th Oct.