To sum Previous data values using built in functions

[#1]

hi,

I am getting the previous month value using variable PeriodN....with below formula

=FIELDVALUE('PeriodName', FIELDINDEX('PeriodName', ONLY(PeriodName))-1)

And in expression

Sum ({$<PeriodName={'$(#PeriodN)'}>}Values)

Is any other possibility to bring the values using the functions fieldvalue,fieldindex in an expression statement itself to find the same sum of values.

without using variable and assigning it,,,