How to get last month Stock balance amount ?

[paulyeo11]

Hi All

I have below expression can give me Stock Balance Amount for Max date :-

=Sum({$<date = {"<=$(=Max({$}[date]))"}, month = >}[Amount])

May i know how to modify the above , so that i can get last month Stock Balance Amount ? This will enable me to compare Current month stock vs last month.

Paul