hi there,

try using 'SET'

SET  vMonthPrevious = MonthName(Today())-1;

also put $(vMonthPrevious) in a text/image object just to be sure its calculating the result in right format.

Even after using SET and reloading, you may still need some adjustments or interpretation/formatting functions to get the equivalence operation in the SET to work as you need.

Count({<Month={'$(vMonthPrevious)'}>}Products)