Set analysis Refer to Dimension

[#1]

Hello,

I'm having 2 tables (In reality there are more columns)

T1: PlayDate, Movie, Hall, ....., Visitors

T2: NPSDate, NPSMovie, NPSScore

We have especially not named the Date and Movie colmuns the same as want we want to achieve is the following ...

In a chart we would like to display the Daily score as wel the running total of the score.

Except, the score has to be calculated each time, same problem as average of averages is not the correct average.

What could solve my calculation problem is by working with a formula.

This Set Analysis works :  Sum({< [NPS Date]={"1/1/2012 12:00:00 AM"},[ZZNPS_GRPF_ID]={"12381"} >} NPS_SCORE)

But now i need to change the static selection to my field/dimension name and as soon as I change (ex) the "1/1/12 " by "=[PlayDate]" things go wrong.

Any suggestions ?

[#2]

Extra Info

Sum({<ZZNPS_GRPF_ID={12381} >} NPS_SCORE)  This Works, but gives on each line the same result (obviously)

Sum({<ZZNPS_GRPF_ID={$(=Only(ZZSYS_GRPF_ID))} >} NPS_SCORE) This doesn't works, although ZZSYS_GRPF_ID is a dimension in this Chart.