Hi Praveen,
If you looking for report Year Month restricted for last three month excluding current month then below would be your universe object.
LastMonthYear=Case When Month(SysDate)=01 Then Year(SysDate)-1 Else Year(SysDate) End
LastMonth=Case When Month(SysDate)=01 Then 12 Else Month(SysDate) End
LastMonthYYYYMM=To_date(@Select(ABC\LastMonthYear)+@Select(ABC\LastMonth);"YYYYMM")
Create condition object as below and use it in the report to restrict data in report for Last 2 Report year months.
=Report_Year_Month Between add_months(@Select(ABC\LastMonthYYYYMM),-2) and @Select(ABC\LastMonthYYYYMM)
Thanks
Mallik