Tariff change but old results must remain untouched

[Leo_Polla_Psemata]

Hi there
Few months ago, with the help of this site, I managed to make a simple VBA code.
The code calculates a tariff based on dates and gives currency results.
On 1st of September the tariff will change.

How can I tune the VBA code to the new tariff without affect the old records??

ps , my VBA knowledge is only rudimentary.

 

[JHB]

You need a table to keep track on when a tariff change, like below, and ofcause change you queries to get the right tariff.