Change field from other field only if there been an history change - retroactive

Change field from other field only if there been an history change - retroactive

Hello,
What I'm trying to do is give a value to a field call "Verified Lost Amount"  from another existing field call "Total Loss Amount" but only if there has been an history change to "Total loss amount" field in the past and I want to do it retroactive to all my leads.

In my mind it could be very easy workflow

      if [field_name] has history change
            add last value from [field_name] to [new_field]

anyway, I have no idea how to create this retroactive.

Would appreciate your help!