Here's how to use Excel events (e.g., Workbook Open) to trigger macros automatically:

1. Accessing the VBA Editor:

- Open the Excel workbook where you want to create the macro.
- Go to the Developer tab (if it's not visible, you might need to enable it in the Excel Options).
- Click Visual Basic in the Code group. This opens the VBA editor.

2. Choosing the Object and Event:

- In the Project Explorer window (left pane), double-click on "ThisWorkbook" or the specific worksheet name where you want the macro to run based on the event.
- In the code window (right pane), use the dropdown list next to "Private Sub" to choose the event you want to trigger the macro. Common events include:
- Workbook_Open: Runs when the workbook opens.
- Worksheet_Activate: Runs when the specific worksheet becomes active.
- SelectionChange: Runs whenever the selected cell changes.
- SheetBeforeClose: Runs before the specific worksheet closes (useful for prompting to save changes).
- And many more depending on the object you choose (ThisWorkbook, Worksheet, etc.).

3. Writing the Macro Code:

- Below the chosen event in the code window, paste or write your macro code. This code will execute whenever the chosen event is triggered.

4. Example (Workbook Open Event):

Here's an example macro that runs a message box saying "Welcome!" whenever the workbook opens:

```vba
Private Sub Workbook_Open()
MsgBox "Welcome!", vbInformation
End Sub
```

5. Running the Macro:

- Save the workbook as a macro-enabled workbook (.xlsm). This is important as macros won't work in regular .xlsx format.
- Open the workbook again, and the macro will run automatically based on the chosen event (in this case, when the workbook opens).

Important Considerations:

- Using events can be powerful, but it's important to be mindful of potential issues like infinite loops or unexpected behavior if your macro code is not well-structured.
- Make sure your code is efficient and doesn't slow down workbook performance.
- Consider using comments within your code to explain its functionality for better understanding later.

By following these steps and understanding the concepts, you can leverage Excel events to automate tasks and enhance your workbook's functionality.