Formula Fields - auto recalculate new formula in historic records?

Formula Fields - auto recalculate new formula in historic records?

I have set up a new formula field in a module. If I open an individual record and then click save  the formula is calculated. But I have 600 old records that I would like to update.  Is there any way I can update them all en masse - i.e. trigger the calculation in the formula field without editing each record individually?