Hi,
My name is Richard and I am from New Zealand. I am going to apply some common sense and assume your website already has a function to make price changes. Your requirement is simply to introduce a mechanism to pre-create the change (e.g. another admin form), set a date and have it automatically apply when the date comes around.
Before you accept my bid, I would appreciate being able to have a quick chat to better assess my bid. Although I'm very confident that I have allowed enough time, it is always nice to get all the information before hand.
Regards,
Richard