lock cell formula result, even if source data changes

[simpson]

I have a workbook that i use daily to figure pricing to our customers. the master sheet has the date and the price, and so do the per day sheets. When i change the date and price on the master i need the price on the corrisponding sheet to lock in and not change.
is this possible?
example;
on master date 1-1-11 price = 3.33
on sheet 2 price = 3.33

on 1-2-11 I change the master price to 3.35
on sheet 2 the price remains 3.33
on sheet the price shows 3.35

thanks in advance