Creating a rolling standard deviation within magic ETL

I'd like to create rolling standard deviation within Magic ETL that uses the previous 90 rows (or previous 90 days) as the window. I was able to do this within MySQL before, however, I'd like to do this within Magic ETL.

For example if I have 100 rows of data each row should reference the previous 90 rows as the sample size for the standard deviation (ex. row 5 would reference previous 5 rows, row 10 prev 10 rows... then once it hits 90 it would reference 90 rows... 91 would be row 2 - 91)

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