O.K I'm not much knowledge on the report generation side, but hope you could do the following.

create a transaction table. with 3 columns: two for the data and one for the flag.

now once afte you do a transaction, put the new values into the tansaction table. Then set the flag to be false. On the next time when you use that value reset the flage and insert a new value. One of the other things that you could add is a date column, such that you can hold a certain period of data and purge the reset (for maintanence reasons).

I hope this would help you to an extent.

Sam