Cannot fetch multiple values from the months filter

[siddharthsoam]

I am using the following expression for to fetch multiple values from the filter (months)

concat(distinct text(Date(Date#(if($(exit_month)=12,$(exit_month)-9,$(exit_month)+3),'MM'),'MMM')),',')

where exit_month is used to compute the last month month from months filter. The expression for exit_month is as follows:

max((If(num(month(date#(Mon,'MMM')))<4,num(month(date#(Mon,'MMM')))+9,

num(month(date#(Mon,'MMM')))-3)),'MM')

The exit_month expression works fine independently but does not work with concat( distinct..