Forum Discussion
Adding new Excel Functions
- Aug 12, 2021
If the function is intended for use in a specific workbook, make sure that you create the code for the function in a standard module in that workbook. A standard module is the type of module that you create by selecting Insert > Module in the Visual Basic Editor.
It won't work if you create the code in the code module of a worksheet or in the ThisWorkbook module.
Make sure that you save the workbook as a macro-enabled workbook (*.xlsm or *.xlsb); if you save it as a .xlsx workbook, all VBA code will be lost.
If the function should be available in all open workbooks, you must create it in your personal macro workbook PERSONAL.XLSB. If you don't have this yet, you must create it by recording a macro in your Personal Macro Workbook:
After that, you can remove the dummy macro that you recorded, and create your own functions.
To refer to a function in your personal macro workbook in a formula, prefix it with PERSONAL.XLSB. For example:
=PERSONAL.XLSB!MyFunction()
or
=PERSONAL.XLSB!MyFunction(A1,A2)
When you quit Excel, it will prompt you to save changes in PERSONAL.XLSB. Answer Yes!
Thank you Hans. That seems very helpful but I still seem to be missing something basic. I have entered the following in a module edit window, as you suggest:
Function Interpolate(lwr, upr, lwrval, uprval, x)
Interpolate = lwrval + (x - lwr) * (uprval - lwrval) / (upr - lwr)
End Function
I have also tried adding "As single" to the first line and both variants compile successfully but neither seems to propagate into my worksheet, which refuses to admit to the existence of a function with the name Interpolate. What am I missing?
- Dicky_g141Aug 15, 2021Brass ContributorFor anyone who is interested in this thread I have found that, by saving my macros in an Excel add-in file (.xalm extension) it propagates into all spreadsheets and the macros can just be used as is, that is without the MYMACRO! prefix.
- LauraKLMay 03, 2024Copper Contributor
Hi,
I'm on Mac OS and still a bit stuck. I'm working with a UDF, not a macro. I can create the function and use it with my current workbook, but it only shows up in my list of functions with the PERSONAL.XLSB! prefix. I would love to not have to type all of that every time and I would also like to be able to reference it from different workbooks. Is this possible on Mac OS?
(Should I create a new post/question for this?)
Thanks in advance

- HansVogelaarMay 03, 2024MVP
If you want to be able to use the UDF without a prefix such as PERSONAL.XLSB! you have to store it in an Excel add-in (*.xlam). See for example Method 3. Create an Excel add-in file
- JKPieterseAug 16, 2021Silver ContributorNote that this isn't true for sharing workbooks using your UDF with a colleague; the location of your UDF is stored in your workbook and if that location is different for your colleague (usually the case!) then the UDF will not work. Hence: https://jkp-ads.com/Articles/FixLinks2UDF.asp
- Dicky_g141Aug 16, 2021Brass ContributorThanks for the warning, Jan. I have no immediate plans to share these functions but, if I do, I shall invite recipients to re-create them for themselves.
As an aside I wanted to award "likes" to both you and Hans for your helpful contributions. However, while I can apparently view likes awarded by others (not that there are any in this thread), there seems to be no way to award them myself.