Getting Prev FinYear MaxMonth figures

[Mothapoe]

Trying to get below expression which displays current FinYear MaxMonth to display Prev FinYear MaxMonth

Variable Name: vDate_MaxYearMaxMonthMaxDay

Expression:

=if(text(Date(MonthEnd(Date#($(vDate_MaxYYYYMMDD), 'YYYYMMDD')), 'YYYYMMDD'))
= text(Date(Date#($(vDate_Global_MaxMonthEndYYYYMMDD), 'YYYYMMDD') , 'YYYYMMDD'))
,max({<CAL_YEARMONTHINDEX = {$(vDate_MaxYEARMONTHINDEX)}>}DAY_NO)
,if(GetSelectedCount(DAY_NO) > 0 , max(DAY_NO),
31))

See breakdown of fields and variables used in attached snipper. Please ignore circled (Red).