Variance between current year and last year in columns

There probably is a way to do that. However, typically, the "Sales Amt" is calculated per a category of sorts. For example, "Sales Amt", per salesperson; store; region; or even date. Does that make sense? If you truly just want "Sales Amt", you could probably do something along the lines of:

ADDCOLUMNS (
    SUMMARIZE ( SalesTable, [CY], [LY], [Variance] ),
    "Sales Amt", "Sales Amt"
)

I would need a better understanding of the data to build that DAX for you.

Lastly, if my response was helpful, marking it as a solution would be greatly appreciated🤠