Manually changing loading date in delivery

Dear Experts

I would like to change loading date in outbound delivery.

we have requirement from our client that he wants to manually change loading date in delivery.

for ex-

as per existing system configuration system shows following data.

if customer requested delivery date is say 20 Feb then system does calculation and propose

pick/pack date- 20 Feb

loading date- 20 Feb

goods issue date-20 Feb

delivery date- 20 feb.

please suggest what we can do to get the desired solution.

Thanks in Advance.

Regards-

Hitesh