Add User Defined function support to the Apps for Office Excel APIs
Add User Defined function support to the Apps for Office Excel APIs so that users can enter formulas in excel. User Defined Functions are one of the most powerful features of Excel (and some competitor spreadsheets products now available in the web). They are critical for us to make our Apps for Office product as powerful as our legacy on premise product.

Yes! We announced GA for Custom Functions @ Build 2019. Please give it a try!
http://aka.ms/customfunctions
33 comments
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Mats I commented
Hi, we're very pleased to hear that the js custom functions will be release. In what Excel build will the custom function feature be publicly released?
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Csbdiqaadir Barwaaqo commented
What's is thhe
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Kevin Thompson commented
Is there any estimate of if/when this will be released to the public? I'm trying to decide between a VBA add-in and a javascript add-in. The latter is preferable, but not if the feature won't be released for a long time.
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Murugananth S commented
Hi Team,
I am trying to implement custom functions in VS2017 but due to manifest error not able to do.
Error : DesktopFormFactor need to use instead FormFactor.
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Anonymous commented
How can we call our own web api call in custom functions?
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Murugananth S commented
Team,
I am not able to use with task pane in sample application. Can you please suggest how to include custom functions in sample application. -
Anwesh Gangula commented
How do we try the developer preview?
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Song Seunggeun commented
Is there any official discussion on the release date of this preview? :)
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Nathan Jackson commented
This is one of the features that's preventing me from beginning to port over a fairly large library of legacy VBA code into JavaScript.
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Tie commented
Hello team, i have seen a tag `custom-functions-excel` in StackOverflow, it seems that there is some update, right?
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Sven Wehmeier commented
Hi team, some update would be really appreciated.
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Doug Jenkins commented
The potential for on-line Excel UDFs is enormous, and the long wait is frustrating.
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We wanted to just give a quick update that we are still working on this. We are hoping to have something in preview later this year.
Thanks!
Office Extensibility Team -
Charles Walker commented
Any news on this topic ?
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Hervy commented
Hi team, some update would be really appreciated.
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Tie commented
Hi team, I was told that there should have been some news around the 12th of May. So is there any update?
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Thorsten Hans commented
hey team, any update on this one?
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Hector David commented
#jirabot
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Anonymous commented
This is going to be a huge on Excel lovers.
Looking forward to an update on this.
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Andy Comley commented
Its hard to see how any addin for Excel can look like its working alongside Excel without this feature. At the moment Excel addins look totally disconnected with the rest of Excel functionality. Users want close integration between addins and Excel - so the ability to hook into the formula mechanism is a key part of that.