In Excel, you can calculate the integral average, also known as a definite integral, by using the "SUMPRODUCT" and "TRAPZ" functions.

Here's an example of how to calculate the definite integral of a set of data using these functions:

- Organize your data into two columns, one for the independent variable (x) and one for the dependent variable (y).
- Determine the range of values over which you want to calculate the definite integral.
- Use the "SUMPRODUCT" function to calculate the sum of the products of the width of each rectangle (dx) and the height of each rectangle (f(x)). The formula for this is: =SUMPRODUCT((B2:B7-B1:B6)/2,(B2:B7+B1:B6))
- Multiply the result from step 3 by the width of each rectangle (dx) to get the definite integral.

Note: The "TRAPZ" function is another option for calculating the definite integral in Excel. The syntax for this function is: =TRAPZ(data_y, data_x). The "data_y" argument is the range of the dependent variable (y) and the "data_x" argument is the range of the independent variable (x). The "TRAPZ" function will calculate the definite integral based on the trapezoidal rule, which approximates the area under a curve by dividing it into a series of trapezoids.

It's important to note that these methods are only approximations of the definite integral and the accuracy of the results depends on the size of the rectangles (dx) and the shape of the curve. To get a more accurate result, you can use smaller rectangles (dx) or use a numerical integration method that uses more sophisticated algorithms to calculate the definite integral.