Question regarding getting column value from previous record and putting in next record

["ganbold" <ganbold@xxxxxxxxxxxxx>]

Hi,

I'm writing in PHP and in perl ISP billing software and I have some problems.
I have following questions:

I need get some column value from previous record and put it to next record column value. It is something like:

                Contract_id    Userid        Previous_balance    Daily    Total    Due_balance
Record 1:    1                   Ganbold        100                    10        10        110
Record 2:    1                   Ganbold        110                    8            8        118

Due-balance=Total+Previous_balance
Previous record's Due_balance is next record's Pre_balance

How to solve this kind of problem in one query? IS there any way to do that in one query or command?
How to solve it in simple way? I need solution which gives me fastest speed.

thanks in advance,

Ganbold