Visual Basic for Applications:
Organizing code into functions

How to:

In VBA, functions are defined using the Function and End Function statements. Here’s a simple example of how to create a function that calculates the area of a rectangle:

Function CalculateArea(length As Double, width As Double) As Double
    CalculateArea = length * width
End Function

To call this function in your VBA code and display the result in a message box, you would use:

Sub ShowArea()
    Dim area As Double
    area = CalculateArea(10, 5)
    MsgBox "The area is " & area
End Sub

When executed, this code displays a message box stating: The area is 50.

Passing Variables ByRef and ByVal

VBA allows you to pass variables to functions either by reference (ByRef) or by value (ByVal). The former means the original variable can be modified by the function, whereas the latter passes a copy, protecting the original variable from changes.

Function ModifyValue(ByRef num As Integer)
    num = num + 5
End Function

Function PreserveValue(ByVal num As Integer) As Integer
    num = num + 5
    PreserveValue = num
End Function

Deep Dive

VBA, as an event-driven programming language, places significant emphasis on functions and subroutines to handle various tasks. Unlike many modern languages, VBA has a unique trait where the Function keyword not only declares a block of reusable code but also allows for an implicit return value directly assigned to the function’s name.

Historically, the design of VBA functions has been influenced by earlier programming paradigms where encapsulation and modularity were gradually being recognized for their importance in software development. This historical backdrop has led VBA to adopt a somewhat conservative yet functional approach to organizing code.

While VBA is powerful within its native environments (e.g., Microsoft Office applications), it’s essential to note that the programming world has evolved. Languages like Python offer more straightforward syntax and a vast standard library, making them a favorable alternative for various applications outside the Office suite. However, when working within Microsoft Office products, the integration and automation capabilities VBA provides are unmatched.

It’s worth noting that despite its age, the community around VBA remains active, continually finding innovative ways to leverage its functionality. Yet, as the software industry moves towards more modern, versatile, and robust languages, programmers familiar with VBA are encouraged to explore these alternatives for non-Office related tasks to broaden their coding toolkit.