Makes it possible for you to specify a calculation to perform on Field control expressions and display the calculation results instead of the expression. You can also specify the point at which to reset the calculation in the report.
Note: 

This tab replaces the functionality of the native Visual FoxPro Calculate Field Dialog Box when the Report Builder is active. 
Calculation type
Specifies additional calculation operations that can be applied to the values of a Field control expression to obtain the value rendered in the output:
Note: 

Cumulative calculations are reset depending on the Reset value based on option. 

None (Default)
No additional calculations are performed. The result of the Field expression is directly passed to the report engine for output.

Count
The value displayed is a count of the number of times the expression has been evaluated for the records traversed thus far. (The Field expression is not evaluated.)

Sum
The value displayed is a running total of the values of the Field expression for the records traversed thus far.

Average
Computes the arithmetic mean of the value of the Field expression for each record traversed thus far and displays the results.

Lowest
The value displayed is the lowest value of the Field expression evaluated for the records traversed thus far.

Highest
The value displayed is the highest value of the Field expression evaluated for the records traversed thus far.

Std Deviation
Computes the square root of the variance of the evaluated Field expression for each record traversed thus far and displays the results.

Variance
Measures the degree to which the evaluated Field expression value varies from the average for the records traversed thus far and displays the result.
Reset based on
Specifies the point at which to reset any cumulative calculations. The default value is "End of Report."
Note: 

If you have specified data groups in the report, Detail bands, or target alias expressions for Detail bands, the Reset based on list displays those items. 