Simple Counter Within a Filter

I have count variable that I need to increment by 1 each time a certain condition is met within a configurable collection filter, then I need that variable to be available outside the filter.

Which component would I use to increment, and do I need to set the count variable as global so it can be acessesed from outside the filter?  (As to my understanding, the only output variable in the filter are the records that were kept in the collection).

Thanks for helping with my beginner questions...