Scripting Problem

Hi Brian,
I have a project that I am working on and wanted to use scripting to do it:
I am performing analysis on a customer transactions database that has deposits that change to a base currency after 30 days if not utilized.
Customer deposits (identified as credits 'C') are utilized according to the order they arrive in, granted they are still within the 30-day limit from the date of deposit.
The idea is to check at the end of a specified date, how much is still viable for use and how much has been converted to a base currency
See dataset sample attached.
Regards.
Tendai