Previous Month expression

[newbie_sm]

I have set the following  expression:

(
Sum({<Month={'$(=Max([Month], 'YYYY-MM'))'}>} Revenue)
/
Sum({<Month={'44927'}>} Revenue)
)
-1

where {<Month={'$(=Max([Month], 'YYYY-MM'))'}>} is Current Month

How can I set a similar expression for calculating Previous Month?  I tried this but it doesn't work:

{<Month={'$(=Max([Month]-1, 'YYYY-MM'))'}>}

[newbie_sm]

In addition, when I used this format

(Sum({<[Month Year]={'$(=Max(Date([Month Year], 'YYYY-MM')))'}>} USD_Revenue) / Sum({<[Month Year]={'$(=Max(Date([Month Year]-1, 'YYYY-MM')))'}>} USD_Revenue)) -1

both months format returned in YYYY-MM i.e. 2023-02 and 2023-01, but the calculation is still not returning properly