Saving Cumulative Data Or Something Like That :)

Hi,
There are 3 tables
Table,
TableDetails,
TableDaily.

With structure

TABLE:

TableID        UserID        Money
----------        ----------        ----------
(int)            (int)            (money)


TABLEDETAILS:

TableDetailsID    TableID        ItemID        PaidForItem    DayID
----------               ----------        ----------        ----------           ----------
(int)                   (int)             (int)            (money)         (int)


TABLEDAILY:

TableDailyID    TableID        PaidForItem    Money        Total                                 Change
----------            ----------        ----------            ----------        ----------                              ----------
(int)                (int)             (money)          (money)      (PaidForItem + Money)       (money)



"Table"    holds id for user and his money amount, which changes during time. "TableDetails" holds data about items user bought, amount paid for them and dayid which relates to one particular day.

"TableDaily" holds history. I do not know how to update this table.
I created job whish runs stored procedure. This procedure sums "PaidForItem" using group by TableID and WHERE DAYID = '11'.

Problem is with Change column. This column sould hold difference between today's Total and previous one etc.

Current procedure looks like this:
INSERT INTO    TableDaily
        (TableID, PaidForItem, Money, DayID)
SELECT        TableDetails.TableID,
                    SUM(PaidForItem) AS PaidForItem,
                    Table.Money,
                    (SELECT    DayID
                    FROM    Days
                    WHERE  (Aktive = 1)) AS DayID
FROM          TableDetails INNER JOIN
                    Table ON TableDetails.TableID = Table.TableID
GROUP BY    TableDetails.TableID, Table.Money