A running total totals all records (in the report, in the group, and so forth) up to and including the current record. For example, if your first three records have values of 2, 4, and 6, the running total for each of the three records would be 2, 6, and 12, respectively. You can use running totals to create customized summaries and totals.
Running totals are a great way to show totals that have a different calculation than a subtotal without having to write additional formulas. Here I am going to explain how to use Running Total Field in crystal report (Visual Studio 2010)
First create the group on the basis of which you want to summarize the data. Here I am selected a product_category field in order to summarize the product details. In order to group the data right click on the Group Name fields and select Insert Group option and then select the field on the basis of which you want to summarize the data and click OK.
After grouping the data, right click on the Running Total Fields option and click on new button.
In the Create Running Total Field dialog box, enter a name for the running total object in the Running Total Name field.
In the Available Tables and Fields area, select the field you want to summarize.
Click the first arrow button to add the field to the Field to summarize box.
In the Evaluate section of the dialog box, click for each record.
In the Reset section of the dialog box, click on change of group and accept the default group name.
Click OK to save the running total field.
Your running total now appears in the Field Explorer, under Running Total Fields.
Either drag the running total field onto the Details section of the report, or, if you want to view a grand total of each group, drag the running total field onto the Group Footer section.
You can see the output or preview of report from Main Report Preview or run an application.