Reprocess all original file

Does anyone know if it is possible to reprocess all files? And How do it? And not one by one?
I have a new field and I would like it to be calculated on all activities.

Many Thanks!

Activity List View, select all or use filters.
Edit - Reprocess files.

Many thanks!!!

If you have just added a new custom activity field you can re-Analyse activities instead of re-process. Its quicker.