how to use the previous row value in the details section further ?

Hi All,

I have a requirement like....

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Header :                                               Previous Month Ending Bal : 9975

Details :

Day       DailyAmount      NetCredit/Debit          EndingBalance    myfield      ABCD

1               100                         25                       10,000            9975            ?

2               100                        -50                         9,950           10,000          ?    

3               100                        -45                         9,905            9,950           ?

4               100                         75                         9,980            9,905           ?    

5               100                       -100                        9,880             9,980           ?

...........

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For Ending Balance, i am using the shared variable from Avelino Fidels's response to Bala on http://scn.sap.com/thread/1871405

But i need to calculate some other values using that "my field" values of which i couldnt able to store anywhere.

In a single sentence my question is to calculate Day 2 ABCD value i need that Day1 Ending Balance value.

Please suggest me some ideas or give me answers whatever you know in this regard.

Thanks in advance.

--Ven G.