Custom Calc of "Scheduled finish" in CO02

Hi Guys,

I would need to make a custom calculation of Date Finish Scheduling based of specific request of my customer.
This vaue is modificable automatically on CO02 -> functions -> schedule -> order with standard calc.

You now if is possible to abbly Custom Formula in User-Exits or Badis?
Alternately, do you think it is possible and appropriate to change this value using standard function module?

Regards,

D.