DAX Variables and where to declare them,

[dicken]

Hello,
I hope someone can gvie me some advice ( reading suggestions ) regarding variables, I'm confused.
So, Variables of defined once, and are constant, but if I use

ab:=VAR maxindex = MAX(Table1[Index]) RETURN maxindex

and then drop that into a pivot table it takes on filter context of the
Pivot table. But sometimes I've had to define the Variable within the iterator,

Copy of Measure 1:=
SUMX(
    Table1,
              VAR aregion = Table1[Regeio
RETURN
               RELATED( Table2[Budget] )    / COUNTROWS(FILTER(ALL(Table1) )
          )

I seem to be misunderstanding somthing? any suggestions or information welcome.

Richard.

 

[dicken]

Hello Matt, sorry this is becoming something of a saga, I think the penny has dropped, I need to declare it as a naked variable,
which is why I need it 'inside' I'm in p pivot so don't have selecedtvalue, I'll try, "if hasone and vaules" just to see if it works" .
Thanks for your patience.
I hae a question coming up re Averages, different methods and efficiency.
Richard.

I did try using
VAR aregion = IF(HASONEVALUE(Table1[Region]),VALUES(Table1[Region]))
but just got back infinity, not the 35000 which is correct, and what declariing within Sumx produces.

Richard