I want to get the the sum of the amount for the selected year and for january up to the selected month. So, If I select 2010 and June, I expect to see the sum of the Amount for 2010 and January to June.
However, this expression is returning me only the selected month.
I cannot change $ to 1, because that will exclude my other selecions (customer type, country, etc).
I imagine that the user is not selecting MonthNumber directly, but rather selecting a field that contains Jan, Feb, Mar, etc. so what you need to do is clear the list that they select first.
