Reference a previous month using variables in DAX using slicers

Last Week Targets = VAR myMax = MAX('Calendar$'[Weeknum]) RETURN CALCULATE(SUM(internetTargets[Impressions]),ALLEXCEPT(internetTargets,internetTargets[weeknum],joinTable[Website],'Calendar$'[Year],'Calendar$'[Month Name]),internetTargets[weeknum]=myMax-1)

Yep got a week number in the date table but it doesnt seem to like using the weeknum function within an evaluation

Anonymous show me your code?

Anonymous will look into later for you

not really sure what you trying to do in that calculation though can you give an explanation before i attempt to rewrite it

Sure,  basically i am trying to sum the previous weeks values.

That calculation gives this weeks value but when I select a dat near the beginning or end of the month the values dont work.  I think it is becasue the slicer sets the table to on the the months selected so the previous week does not work.

ok just that your code looks a bit stranger to me i am not sure what you doing

Last Week Targets = VAR myMax = MAX('Calendar$'[Weeknum]) RETURN CALCULATE(SUM(internetTargets[Impressions]),ALLEXCEPT(internetTargets,internetTargets[weeknum],joinTable[Website],'Calendar$'[Year],'Calendar$'[Month Name]),internetTargets[weeknum]=myMax-1)

firstly it looks like you using 2 tables, is the week number in the calendar table?

secondly your relationships between your date table and internettargets is there one?

essentially though you need to be doing a filter something to this effect

Last Week Targets = VAR myMax = MAX('Calendar$'[Weeknum])

RETURN CALCULATE(SUM(internetTargets[Impressions]), filter('Calendar$', 'Calendar$'[Year]' = Year(now()) &

mymax='calendar'[weeknum]-1)

am sure this isn't right but need to know more about how your data is structured

Yep 

three tables 

one contains date

two contains internet page impressions targets

three contains ga page impressions

There is a week num column in each table and 2/3 joins the calendar table via the date column

Tried what you suggest but it throws up the error

MdxScript(Model) (9, 73) Calculation error in measure 'GA'[Last Week Targets]: DAX comparison operations do not support comparing values of type Integer with values of type Text. Consider using the VALUE or FORMAT function to convert one of the values.

All values are whole numbers.....

After some more testing it seems it does not like the YEAR function