I'm new to Tableau (SQL Vet) and am trying to lookup a previous value (Officer Name in my case). Essential I'm doing a migration analysis to see what assets have transferred between our officers from the previous month to the current month. My dataset is isolated to the last 2 months so I only have 2 monthly data snapshots available. I've created a "Previous Officer" field using Lookup(attr([Officer Name]),-1), which appears to be valid. I also have a True/False statement to identify those assets that transferred officers from the prior period using [Previous Officer] != ATTR([Officer Name]) AND NOT ISNULL([Previous Officer]). My worksheet is filtered to only include the 2nd of the 2 months in my dataset to filter out the first month; however, my results look incorrect. Can anyone help me troubleshoot why my results look incorrect or share how they have a created a month over month migration/change analysis?

Much Appreciated!

Matt