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 allows search and replace in VBA code

Good news: As of now, Flexfind allows you to Search and replace in VBA too!

Mon, 13 Mar 2023 10:55:00 GMT

New: Flexfind JavaScript edition

Good news! Today my brand new Flexfind (JS edition) has been approved for the Microsoft Office Add-ins store!

Thu, 19 Jan 2023 16:45:00 GMT

Update: RefTreeAnalyser

RefTreeAnalyser has just been updated to version 3.1, build 190. Fixed a bug that caused run-time errors when using the Check Formulas option. Made the dialogs compatible with screen reader software for the visually impaired. First build that is Mac compatible!

Thu, 12 Jan 2023 15:55:00 GMT

Updated: An MSForms (all VBA) treeview.

Our All VBA treeview control has been updated to version 26.5. It has been improved for accessibility and is now compatible with the Windows Narrator screen reader (for the visually impaired).

Tue, 10 Jan 2023 15:45:00 GMT

Updated two tools: GithubVBAExporter and FollowCellPointer

I've Updated two tools today: GithubVBAExporter and FollowCellPointer. Find them on the download page.

Wed, 14 Dec 2022 14:30:00 GMT

Update: RefTreeAnalyser

RefTreeAnalyser has just been updated to version 3.1, build 189. If your formula returns a range reference (like the XLOOKUP function does), RefTreeAnalyser will display to which cell(s) the formula points.

Wed, 02 Nov 2022 12:45:00 GMT

Video: Office Script And Power Automate Demo

I presented during the Excel Virtually Global conference October 17, 2022, Here's the recorded video: Office Script And Power Automate Demo

Mon, 17 Oct 2022 08:00:00 GMT

Excel Invoegtoepassingen werken niet

Een beveiliginsupdate heeft ervoor gezorgd dat Office bestanden met VBA code die je download (waaronder ook invoegtoepassingen) niet meer werken. Dit artikel laat zien hoe je dit probleem oplost.

Wed, 12 Oct 2022 09:25:00 GMT

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