Creating running totals using a formula
If you have suppressed data, or your data is based on a formula that occurs WhilePrintingRecords, you should create a running total formula rather than using the Create Running Total Field dialog box.

When you create a running total manually, you need to create three formulas:

A summary formula.
A reset formula to set a variable to zero.
A display formula to display the variable.
In the following procedure, you will create a report that performs the following functions:

Maintains a running total of customer orders.
Groups customer orders and resets the running total for each group.
Displays the subtotal for each order (the last running total for that order).
To create running totals using a formula
Create a report using the sample data, Xtreme.mdb. Link the Customers and Orders tables and place the following fields from left to right in the Details section:
{customer.CUSTOMER NAME}


{orders.ORDER ID}


{orders.ORDER AMOUNT}


On the View menu, click Field Explorer.
Select Formula Fields in the Field Explorer dialog box and click New.
Name the formula "RunningTotal" and click Use Editor.
The Formula Workshop appears with Formula Editor active.

Enter the following into the Formula box:
WhilePrintingRecords;


CurrencyVar Amount;


Amount := Amount + {orders.ORDER AMOUNT};


Click the Save and close button on the Formula Workshop.
Place this formula in the Details section of your report, just to the right of the {orders.ORDER AMOUNT} field.
This formula prints the running total of the values in the Order Amount field.

On the Insert menu, click Group and group the report on the {customer.CUSTOMER NAME} field.
In the Formula Workshop, create "AmountReset":
WhilePrintingRecords;


CurrencyVar Amount := 0;


This formula says:

Set the value in the Amount variable to 0.

Place this formula in the Group Header #1 section of your report.
Because the Group Header #1 section appears once for every group, @AmountReset will execute each time the group changes. Thus, the Amount variable is reset to 0 each time a new group begins.

Select the @AmountReset formula on the report and use the Format Editor to suppress it so that it will not appear in the final print-out.
In the Formula Workshop, create "AmountDisplay":
WhilePrintingRecords;


CurrencyVar Amount;


This formula simply displays the current value of the Amount variable at any time.

Place this formula in the Group Footer #1 section of your report.
Because the Group Footer #1 section appears once for every group, @AmountDisplay will execute each time a group ends. Thus, the value stored in the Amount variable will be printed each time the group changes.



Note: This formula prints the same value that @RunningTotal prints as the running total for the last record in each group. But since it is printing it in the Group Footer section, it acts as a group subtotal, not as a running total.

On your report, each row in the running total column displays the current record value added to the previous values. The running total starts fresh with each new group, and the final running total for each group becomes the subtotal for that group.

Поищите эту статью в хелпе к Crystal Report, в десятом она находится Runing Totals-Creating running totals using a formula. Возможно на основе этой статьи можно достич желаемого.