Month to date sum based on selected date

[#1]

Hi I am wanting to sum the total revenue we taken within a month, based on any selected date.

I currently have use set analysis to sum mtd up until yesterday:

sum({<[BudgetL1L2 Date]={">=$(=Monthstart(date(today()-1)))"}>} [Revenue Net])

However i am stumped as to how i cam amned this to base it on any selected date.

Does anyone have any ideas?

Many thanks

Kate

[#2]

This is an example  using variables, make sure you make first Variables with this names then try it!!

=

SUM({<Year={'$(vMaxYear)'},Month={'$(vMaxMonth)'},Day={'<=$(vMaxDay)-1'},Date=,MonthYear=>}Amount)