Hi Sriram! Try putting months and years into your columns shelf. Then, put something like this into your Text mark:
LOOKUP(SUM([Your Measure]), -1) - SUM([Your Measure])
This uses table calculations to compare different cells.
Are you using parameters?
Best way to do this is creating parameters for year and month and create calculations for mtd actual and previous. Doing it you also can calculate YTD.