Sum of two years difference

[karla_gonzalez]

Hello,
I have to subtract an amount for the current year vs. the previous year:
I already try these formulas but I have not succeeded.

Sum({<Ejercicio += {{$(=Max(Ejercicio))}>}, {$(=Max(Ejercicio)-1)>}}>} Saldo)

Where Ejercicio is 2017 y 2018 example.

[swuehl]

Maybe

=Sum({<Ejercicio = {$(=Max(Ejercicio))} >}  Saldo)

-

Sum({<Ejercicio = {$(=Max(Ejercicio)-1) >} Saldo)