How to display 3 months values based on field selections

[NavinReddy]

Dear Experts,

I need display 3 months values based on Metric_Month field selection. im using below expression to show the numbers, not sure where im doing wrong its not working as expected. Any suggestions please. 

Count(DISTINCT{<Month=,Metric_Month={">=$(=Date(Max(Metric_Month)-2,'MMM YYYY'))<=$(=Date(Max(Metric_Month),'MMM YYYY'))"}>}trigger_id)

Metric_Month

Aug 2020

Sep 2020

Oct 2020

Nov 2020

Regards,

NR

[NavinReddy]

Any Suggestions please