analysis for periods

[#1]

Hello everyone,

i have tried  work in a indicator of a health industry, in one of this indicator i need a filter that count every patients that have a new episode in the database, and also is active in a other database, something like this:

Patient: Pepita Perez

episode date: 20120302

period of activation: 20120203  to 20120301

this person isn't count in my indicator, because she doesn't active.

i tried to do this:

count({<  episodeDate = {$(='>='& DateBegin)}

            ,episodeDate  = {$(='<='& DateEnd)}

          >} patient)

but, didn't work  

i'm new of this kind of proyect, please help me