You need a query, qryRunningSum_Simple, like this :
SELECT T1.Description, T1.Cost,
(SELECT SUM(Cost) FROM tblMyDollarTable AS T2 WHERE
T1.Cost<=T2.Cost) AS [Acumul Value]
FROM tblMyDollarTable AS T1;
Mind you, you'll have to type this in the SQL window.
And one note of caution - if you have duplicate costs,
you'll get the same Acumul Value for each record with the
same cost. If you have a number field for sorting
records, then you can get accurate results. If your table
looked like this:
RecordID Description Cost
1 Red Truck $8.00
2 Blue Truck $7.00
3 Green Truck $7.00
4 Purple Truck $6.00
then the query, qryRunningSum_Correct, should look like
this:
SELECT T1.RecordID, T1.Description, Max(T1.Cost) AS Cost,
(SELECT SUM(T2.Cost) FROM tblMyDollarTable AS T2 WHERE
T2.recordID<=T1.RecordID) AS [Acumul Value]
FROM tblMyDollarTable AS T1
GROUP BY T1.RecordID, T1.Description;
which will return this:
RecordID Description Cost Acumul Value
1 Red Truck $8.00 $8.00
2 Blue Truck $7.00 $15.00
3 Green Truck $7.00 $22.00
4 Purple Truck $6.00 $28.00
The first query, qryRunningSum_Simple, returns this:
Description Cost Acumul Value
Red Truck $8.00 $8.00
Blue Truck $7.00 $22.00
Green Truck $7.00 $22.00
Purple Truck $6.00 $28.00
Both Blue Truck and Green Truck have the same Acumul
Value, the one thet belongs to the later (the last) of
same value records.
I hope this helped.