VBA stands for Visual Basic for Applications, a programming language by Microsoft implemented for Microsoft applications such as Microsoft Word, Excel, PowerPoint, etc. VBA programming allows automating tasks of nearly every keyboard and mouse interaction between a user and Microsoft Office applications. Macros are Microsoft Office applications that contain embedded code written in a programming language known as Visual Basic for Applications (VBA). It is used to create custom functions to speed up manual tasks by creating automated processes. One of VBA's features is accessing the Windows Application Programming Interface (API) and other low-level functionality. For more information about VBA, visit here.

Now create a new blank Microsoft document to create our first macro. The goal is to discuss the basics of the language and show how to run it when a Microsoft Word document gets opened. First, we need to open the Visual Basic Editor by selecting view → macros. The Macros window shows to create our own macro within the document.

In the Macro name section, we choose to name our macro as THM. Note that we need to select from the Macros in list Document1 and finally select create. Next, the Microsoft Visual Basic for Application editor shows where we can write VBA code. Let's try to show a message box with the following message: Welcome to Weaponization Room! We can do that using the MsgBox function as follows:

Sub GSR()
    MsgBox ("Welcome Back! GSR")
End Sub

Finally, run the macro by F5 or Run → Run Sub/UserForm.

Now in order to execute the VBA code automatically once the document gets opened, we can use built-in functions such as AutoOpen and Document_open. Note that we need to specify the function name that needs to be run once the document opens, which in our case, is the THM function.