Referencing previous row in column: Performance issues

Hi, I would like to create a calculated column that references the previous row (in respect to a date/time column). I have a solution, but it requires too much computation to finish (I am running the column on 24 million rows, it has been calculating for 15 hours).

I have included a table below as an example, [Goal Column] is the column I am trying to calculate. As you can see, it is referencing the [hook_load] for the prior [Regular Date Time.1] (which also happens ot be the prior row in the sorting of this example table). 

I've also included a screenshot of my currently existing code (which takes too long). It's still calculating so I can't include a text version. 

Thanks in advance, I appreicate your support!