# Why is Excel User Defined Function not working?

Encountering issues with your Excel User Defined Functions? Check out our guide to common problems and solutions to get your formulas working smoothly.

Encountering issues with your Excel User Defined Functions? Check out our guide to common problems and solutions to get your formulas working smoothly.

Solving the Excel User Defined Function Not Working?

If you use Excel, you may have heard of User Defined Functions and custom formulas created to perform specific tasks. But what happens when your Excel User Defined Function not working, and you can't figure out why?

Don't worry, we're here to help!

In this article, we'll explore some common reasons why Excel User Defined Functions might not work and provide real solutions to help you fix the issue.

So, whether you're a student trying to complete a math assignment or a professional using Excel for work, keep reading to learn how to solve why is your Excel User Defined Function not working!

## What is User Defined Function, and why does this happen?

User Defined Functions (UDFs)are custom functions allowing you to perform a calculation tailored to your needs.

Basically, you write a little piece of code in VBA (Visual Basic for Applications) that tells Excel how to handle your custom calculation. And the best part? You can input all kinds of data, including:

• Numbers
• Text
• Dates
• Booleans
• Arrays

The output can be anything from a single value to an entire array of values.

But here's the catch: when you update your workbook, Excel only recalculates the formulas linked to the changed cells. And since Excel can't validate the VBA code behind your custom function, it might not know which cells could also affect the result of your custom function.

So, if you're not seeing the correct output from your custom function, it might be because Excel isn't updating it automatically.

Luckily, you can do a few things to ensure your UDFs are working correctly. By understanding how Excel handles custom functions, you can troubleshoot and fix any issues you encounter and get your calculations back on track.

### Volatile and Non-Volatile Custom Functions in Excel

Custom functions are a powerful tool in Excel that allows you to create your own formulas to do all kinds of calculations. But did you know that not all custom functions are created equal? Some are "volatile," while others are "non-volatile."

Here's what that means: a non-volatile custom function only recalculates when the value of its used cells changes. So, if you create a custom function that pulls the name of your workbook, like in our example, it will only update when you change something in the workbook that affects the function's output.

For example: If you change the workbook's name, the function won't update automatically, and you'll be left with the old name.

This can be frustrating if you're using the custom function to display dynamic information, like the current date or time. In those cases, you'll want to use a "volatile" custom function, which recalculates every time Excel does, even if the input values haven't changed. That way, you can be sure that your function is always up-to-date.

Custom functions are a powerful tool for Excel users of all levels, and understanding the difference between volatile and non-volatile functions can help you create more effective and reliable formulas.

### Why Custom Functions May Not Appear in Excel Dropdown List

Have you ever tried to use a custom function in Excel only to find out that it doesn't appear in the dropdown list like the standard functions? This can be frustrating, but there are a couple of common mistakes that can cause this situation:

1. If you're using Excel 2003-2007, you won't see custom functions in the dropdown list. Custom functions are only available in newer versions of Excel.
2. The custom function must be written in a standard VBA module called Modules. When you create a new module to write the function code, a Modules folder is automatically created where all modules are stored.
3. Sometimes a new module is not created, and the custom function code ends up in the wrong place, such as the code area of a worksheet or workbook. This will cause the function to not work or appear in the dropdown list.

So, if you want to use custom Excel functions, always write the code in the Modules folder. This will ensure your custom function works as intended and is easily accessible in the dropdown list.

### User Define Function is not yet enabled

To use User-Defined Functions (UDF) in Excel, you must first enable the Developer tab in the ribbon.

To do this:

1. Go to the Excel Options
2. Customize the ribbon
3. Check the Developer box on the right-hand side

Once you enable this option, you will see the Developer tab appear in the ribbon, where you can start creating and using your own custom functions.

In this list, we'll review ten different things to check when your UDF isn't working:

1. Check for errors: Before using the UDF, double-check the any errors preventing it from working. Even a small typo can cause the function to fail.
2. Ensure the function is saved in the correct location: Make sure that the function is saved in the correct folder and format. If it is not saved properly, Excel cannot recognize and use it.
3. Ensure the function is enabled in Excel: If the UDF is not enabled in Excel, it will not work. You can enable it by going to the Excel options and checking the "Developer" box.
4. Verify that the function name is correct: Ensure that the function name is spelled correctly and matches the name used in the formula. Any discrepancies can cause the function to fail.
5. Check if the function requires specific input parameters: If the function requires specific input parameters, ensure that the data you are using matches the required format. Otherwise, the function will not work correctly.
6. Ensure that the function is compatible with your version of Excel: Some UDFs may not be compatible with certain versions of Excel. Check the compatibility before using the function.
7. Check if the function uses invalid arguments: Make sure that the function uses valid arguments that Excel recognizes. Invalid arguments can cause the function to fail.
8. Ensure the function has the correct return value: If the function returns an incorrect value, double-check the function's code to ensure the correct value is returned.
9. Check for circular references in the formula: Circular references can cause the function to fail. Check for any circular references in the formula and resolve them before using the function.
10. Verify that the function is not blocked by antivirus software: Some antivirus software may block the use of UDFs. Check the antivirus settings and add an exception if necessary.

### How do I force UDF to recalculate in Excel?

You can use a simple keyboard shortcut to get Excel to recalculate a User Defined Function (UDF). Press Ctrl + Alt + F9 to force all functions in the worksheet to recalculate.

It's important to note that for this to work, your UDF must be marked as "volatile". When a function is marked as volatile, it will recalculate automatically whenever a cell is recalculated or changes to the workbook.

Recalculating your UDF is essential to ensure that your calculations are accurate and up-to-date. This is especially important when working with large amounts of data and complex formulas.

Without proper recalculation, you may encounter errors in your calculations that could have significant consequences.

By using the Ctrl + Alt + F9 shortcut, you can easily force Excel to recalculate your UDF and ensure that your calculations are accurate.

## Final Thoughts

There are several reasons why a user-defined function in Excel might not be working. These can include syntax errors, incorrect function location or name, incompatible input parameters or Excel versions, circular references, and blocked antivirus software.

To ensure that your custom function works properly, make sure to check for these common issues and follow the suggested solutions. With the correct setup and troubleshooting, your user-defined function can provide a valuable tool for your Excel calculations.