Filter listbox values

[#1]

Hello

How do you filter listbox values?

Eg:

I have a listbox containing customers.

Lets say i have from A to Z customers:

A

B

C

D

E

F

G

and so on.

But in my charts there is only data for A,B,D.

So i want my listbox only to show A,B,D and not all the others because they dont have any data on them.

I would think something like this, but it is not working:

=if(sum({$<"[DimCustomer].CustomerName"=>} "[FactQVTimeRegistered].TimeRegistered") >0,"[DimCustomer].CustomerName", null())

[nizamsha]

aggr(only($ {<fieldname={'a','b','c'}>}fieldname),fieldname)

[#3]

brillant.

What does the aggr and only do? Why cannot i use sum?