Filtering mail from a saved folder.

Hello,
        If I have a saved folder, and want to extract mail from it 
based on From: field and save it to another file or re-direct it to
/dev/null is there any simple way to do it? 

        I know procmail works on incoming mail but, will it also
work on saved folders?

        I have some huge folders whih I cannot open from elm or pine
due to space constraints.

Thanks ...
Charlie.