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Welcome to the website of JKP Application Development Services

What I do


I offer services pertaining to any aspect of Excel and VBA. My Services page shows you examples of services I provide. You will also find a list of recent projects there.


I develop bespoke Excel tools for customers and also Excel add-ins for the general public, like my spreadsheet auditing tool RefTreeAnalyser. Check out products I have developed.


I offer both pre-scheduled trainings and custom-made courses. Content of trainings can be adapted to your needs. If preferred we also offer any course as an in-house training.


Subscribe to our news letter or check out the archive. There is no set frequency, I just post something when I have time. In any case, it is all about Excel.

Free Excel tools

I develop custom-made applications using Microsoft Office Excel® and VBA and Access and VBA to their full extent. Have a look at various (free) downloads, some of which have become the de facto standard for Excel developers around the world.

Who is Jan Karel?

Would you like to learn more About me? On this page you can get to know me a little better and also find a short list of presentations I've given over the past years.

What's new on this site

English and/or Dutch content

Office Script, enkele voorbeelden
Sinds Juli 2020 kunnen Microsoft 365 gebruikers hun acties in Excel laten opnemen als Office Script macro's. Eerder plaatste ik al een artikel dat laat zien hoe je hiermee start. Op deze pagina toon ik wat voorbeelden van Office scripts die je niet kunt opnemen met de Script recorder, maar die wel nuttig zijn.
Thu, 26 Aug 2021 13:05:00 GMT

Office Script, some examples
Since 2020, Microsoft 365 users can record their actions in Excel on-line into Office Script macros. This article shows example scripts which you cannot record but might come in handy.
Tue, 24 Aug 2021 15:45:00 GMT

Update: RefTreeAnalyser
RefTreeAnalyser 2.0 has just been updated. Fixed an issue with the links on each sheet back to the ToC.
Fri, 20 Aug 2021 13:30:00 GMT

Update: RefTreeAnalyser
RefTreeAnalyser 2.0 has just been updated. Added Tables to the table of content option.
Tue, 17 Aug 2021 17:20:00 GMT

Update: RefTreeAnalyser
RefTreeAnalyser 2.0 has just been updated. Added Form and ActiveX controls to the table of content option.
Fri, 13 Aug 2021 16:10:00 GMT

Importing Text Tiles In An Excel sheet
A long time ago I wrote an article about how to best import text files into Excel. I've updated the article today to include the PowerQuery steps.
Wed, 11 Aug 2021 15:00:00 GMT

Getting rid of the "cannot find your add-in" message
Many users struggle with getting rid of an Excel add-in. In this article I show how to fix the infamous "Sorry, we could not find..." error message.
Wed, 14 Jul 2021 14:45:00 GMT

A self-installing add-in
Many users struggle with getting an add-in installed. In this article I show some VBA code that will ease that process: As soon as the user opens the add-in and enables macros, the add-in offers to install itself.
Mon, 12 Jul 2021 13:40:00 GMT

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