Dynamic Date

[#1]

Hi I am trying to get a dynamic date for an expression I am building.

We use Set Analysis so my code is

sum({$<
[Bill Date]= {"<=$(=date(max(Date)))>=$(=date(min(Date)))"},
Year = {'2016'},
Period = {*},
Date = {*},
Month = {'Aug'},
[Calendar Year] = {*},
QuarterName = {*},
[LinkId] = {"FIN"}
>}
[Bill Value] * $(RevenueRate))

which is perfect for August 2016 but no good for any other dates. In September I would like to report for all of August and in October I would to report for September etc.

I can get the current month using ={month(Max([Bill Date]))},

But I can't put this in the expression.

Any help would be gratefully appreciated

[#2]

I used

Sum({<[Bill Date]={">=$(=MonthStart(Today(),Day(Today())=1))"} ,
thanks for your help