If you are trying to use array formula for retrieving, say sum of all values within the multi-select, you can use PALO.DATAV to sum the values across the array. So, the format would be: =SUM(PALO.DATAV(DB,Cube,Element,Element,Array,...,Element)) Hope this helps.
You can use a list box without a dynarange also. However, it becomes a very static report. The thing is that (in case of a multiselect list box) the output is an array, and hence, dynarange is a good option to use. If you do not want to use dynarange, you can use array functions like index. Please see attachment.
If you need this information on a report (not necessary using rules), why don't you use subsetsize with a data filter? Easy way to get this is to create a subset and then change the formula from subset to subsetsize. More details at: knowledgebase.jedox.com/knowledgebase/jedox-olap-functions/ Regards, Kiran