It started with the Yellow Pages
In 1995, Ruud Coopmans left his employer. Not out of ambition to start a business, more out of unease: "I'm an individualist, and independent too. After working for several employers, I concluded that I didn't fit well in a large company."
He picked up the Gouden Gids — the Dutch Yellow Pages — and looked under C for computer training. Maybe he could start giving courses.
The timing turned out well. Windows was on the rise, Lotus 1‑2‑3 and WordPerfect dominated the office, and training institutes were looking for freelance instructors for corporate courses. Ruud taught courses where people learned to click, double-click and drag. Fairly dull, he admits — but he found the Lotus course interesting, and students noticed.
That's how the real work began. "Could you come and take a look at my workplace — we have a problem with our planning, or our calculations." The first assignment was a calculation for a company in Boxmeer.
On 4 March 1996, ExcelSpecialist was registered with the Chamber of Commerce. Over the thirty years that followed, Ruud worked for over six hundred clients, from sole traders to large organisations, spread across the Netherlands and Belgium.
What changed the work
The change with the biggest impact was one most users barely noticed: the moment an Excel file could contain more than one worksheet.
"You no longer had to limit the number of sheets or cram everything onto one sheet — you could organise it logically. And organising it logically also makes the program code relatively easy to write. So the more clearly you structure something, the easier it becomes for you and, in turn, for the client."
That's the whole approach in one sentence: structure first, so everything after it gets easier.
The problem that kept coming back
Asked what he has solved most often over the years, Ruud lands on reports. Data coming out of an ERP system, assembled by hand, and repeated every single month.
Clients who spent five days a month on it saw the processing reduced to one click and a minute. The reaction was always the same: we should have known this sooner.
The principle
Ruud's most important rule isn't technical but organisational. Every solution has three roles — a user, an administrator and a developer — and the three are kept separate. The user can enter data and can't break anything. The administrator can configure. The developer can build. "It has to be a foolproof application."
There's a lesson that goes with that, learned from experience. A client who says that appearance matters more than security sounds reasonable. But indulging that wish too far makes things harder for everyone — the client first of all, the moment someone accidentally overwrites a formula that no one can bring back.
The rest comes down to two things: honouring agreements and respecting the client. If something can't be done, the client hears that honestly and on time.
How Dennis joined
In 2008, Dennis Spoelder worked as a supply chain manager at a wholesaler in Eindhoven. He had built an order confirmation system in Excel himself. It worked, but the user, administrator and developer roles were not separated, and security was inadequate. He asked his manager for permission to bring in a professional.
That turned out to be Ruud. It clicked — both thought logically and kept things straightforward — and they stayed in touch. Eighteen years on, that company is still a client.
What's changing now
Ruud is stepping back. Since 2026, ExcelSpecialist has been a trading name of Jazetti B.V. Same way of working. The phone number is new: you can reach us on +31 6 10 100 843. Ruud remains available for ongoing projects and for advice.
His own closing word to his clients: thank you for your trust, and with Dennis you're in good hands.
About Dennis
I am Dennis Spoelder, co-founder of Jazetti B.V. and a builder of Excel-VBA applications since 2008. Ruud Coopmans taught me the craft; I hired him in 2008. I now carry ExcelSpecialist forward.
I did not start out as a programmer. My background is logistics and supply chain, where I was responsible for processes and teams. When the available software did not fit, I started building it myself. The sequence has never changed: understand the work first, then address the technology.
Since then I have built business-critical applications that are used every day — from a single user to thousands, with a multilingual interface. I develop with AI assistance, within firm rules for build, validation and delivery. The main benefit is not speed: documentation, test cases and a structure another developer can take over are included in the delivery, rather than treated as extra work. People still make the decisions.
You have one point of contact: me. I build your application and I stay responsible for the work, including when I bring someone in.
Questions about the handover or an ongoing project?
Feel free to get in touch with Dennis.