EI Dynamic Filtering in APD
To explain a little bit about why dynamic filtering cannot be used easily in APD
Analysis Process Designer does not have the same capabilities as OLAP processing with regards to filtering. Variables in general are not handled
Handling Dynamic Filters
The function module RSAN_PROCESS_EXECUTE is used within APD. This function module does not have any control parameters which could be used for handling dynamic filters in within APD.
The passing of variables is not possible in analysis processes. In some cases, you can use ABAP routines for a dynamic filtering but this must be coded bespokely - SAP does not provide this code. The filter criteria is prepared in another program, and then the results are used in an ABAP routine within the analysis process. You would need to store the results between the nodes of the APD.
Variables like "previous period" are sometimes evaluated directly in the analysis process, but this also entails coding with an ABAP routine.