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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

Updated : Flexfind
Flexfind has been updated: Now allows search in threaded comments.
Mon, 06 Dec 2021 14:35:00 GMT

Office Script, The basics updated
I've updated this article with the new feature to start a script from a button on a sheet.
Tue, 30 Nov 2021 10:55:00 GMT

Office Script, De basis is bijgewerkt
Ik heb dit artikel bijgewerkt met een nieuwe optie om een script te starten middels een knop op het werkblad
Tue, 30 Nov 2021 10:55:00 GMT

Updated: Compare Two Tables
I've updated the tool with some UI improvements.
Mon, 15 Nov 2021 10:15:00 GMT

Update: RefTreeAnalyser
RefTreeAnalyser 2.0 has just been updated to build 170. Improved sorting of chart series nodes on Objects dialog and fixed truncation of some labels on dialogs.
Wed, 10 Nov 2021 10:45:00 GMT

A tombola, built in Excel
Excel is a very serious and powerful business application. That doesn't mean we can't have some fun with it. This file shows how to use circular references to have a tombola, no programming involved!
Fri, 29 Oct 2021 13:45:00 GMT

Updated: ExportVBAProject
I have updated this utility today. It now enables you to get a list of the properties of all userforms (including all their controls) appended at the end of the textfile. ExportVBAProject writes the components from a VBAProject to a single text file. Very useful if you need to compare the VBA code of two Excel files. Use a text compare tool like ExamDiff to compare differences in the exported files.
Thu, 28 Oct 2021 15:45:00 GMT

Updated: Compare Two Tables
I've updated the tool so it also works on files stored in Sharepoint or OneDrive.
Wed, 20 Oct 2021 09:45:00 GMT

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