I have three different sheets containing columns A-SHEET 1,B-SHEET 2,C-SHEET 3 and each sheet containing parameter YTD/MTD I need a column which contains difference of sheet 1 and sheet 2 in sheet 4 & sheet 1 and sheet 3 in sheet 5 according to MTD/YTD.

Good mornings @Ram Prasath Tirunelveli Ramalingam​ 

Your post provides no information on how you bring the data into tableau and how the sheets are connected - leaving us to guess - I would union the sheets to create a single file the pivot the "Columns" to get the data into the proper structure - and use one of the methods shown in https://jimdehner.com/2021/08/22/5-ways-to-do-yoy-and-ytd/ to do the YTD and MTD

you should also see the free training at https://www.tableau.com/learn/training/20214 the first few segments are on data prep and connections

if you run into questions post them here with your TWBX workbook so we can see what you have done - we would be able to be specific at that point

Jim