Thanks for the solution. Sorry I should have said I am looking to compare the number of entries each month between a FY and the FY before. ie. Jul 2017 vs Jul 2016.
I tried Lookup(Sum(Number of Records), -12) and it works when I show all the FY. Problem is I only want to display a year at the time. If I use the filter list to filter data by FY then I lost the last FY. Is there anyway around that?