Running Sum (Complex) with Variables

[Aratie]

I am working in Access 2007.

The following thread is interesting, although my problem is more complex ie http://bytes.com/topic/access/answers/828972-complex-running-totals-ms-access-2003-query .

I will modify my problem to suit this one as they are comparable. Therefore I have a table recording the time created, contributions and interest rate per transaction. I need to know the running balance on a transaction for transaction basis.

Problem 1: My Date Field includes year, month, day and time. The date value is not sequential, in other words a record can be added at any given moment, although the time is unique. I have solved the problem by creating a ‘Auto Number Running Sum’ – Is this correct.

Problem2: Assume I have a field called Rate which gives the interest rate for that record. This interest rate fluctuates.

The AutoQuery Example: QtyContrAutoNo -
Auto DateCreated Contr. Rate
1 2011/01/27 01:27:50 PM $100 0
2 2011/02/02 03:05:33 PM $125 5
3 2011/02/05 02:22:30 PM $150 17
4 2011/03/05 04:59:50 PM $175 13

The Second Query Result:
Auto DateCreated Contr. BalancePerRecord
1 2011/01/27 01:27:50PM $100 $100
2 2011/02/02 03:05:33PM $125 $230 [which is (100*1.05)+125]
3 2011/02/05 02:22:30PM $150 $419.10 [which is (230*1.17)+150]
4 2011/03/05 04:59:50PM $175 $648.58 [which is (419.1*1.13)+175]

I am a novice programmer and I learn by example. After many days searching the web eg. Running Sum, DSum, DLookup and Sub queries – none of the examples carry the balance over to be used in the next record query calculation. Until I found this excellent tread. Now I need to understand the more complex calculation on my problem.