I'm just wondering about possible approaches where you want to calculate a field based on certain values (take as an example, calculating VAT on a sale). However, the rate of VAT may change in the future. If it does change how do you prevent existing records being recalculated while new records use the new rate?
You could use a "if , else" script that changes number field only if it is blank, othrwise do nothing when some field is edited. Have not experimented with dynamic/static variation calulations but might be worth checking.
No need to worry!
Go to form designer.Change your formula in the calculation field.Upon closing the formula editor it will ask you if you want to apply this new formula for the earlier records. Say 'no'. You are done.