Hi,
in this case create one object with Month & Year data type is Date.
Month/Year Object
to_date(CONCAT(@Select(Date\Calendar Month),@Select(Date\Calendar Year)),'MM/yyyy')
After that create condition.
@Select(Class\Month) between add_months(@Prompt('Enter Month/Year','D',,mono,free),-13) and @Prompt('Enter Month/Year','D',,mono,free)
Amit