Access to previous payrun without affecting data Merged

If we have finalised and there is an error - to open up the payroll on staffology you cannot just change one person's info (as you could on PAYEMASTER). Any manual changes done on that payroll will be lost. In the care sector we do not have salaried people so everyone has a manual entry this time. To amend one error would me re-inputting everyone's data again. Why does it have to be like this - PAYEMASTER was so much better.