About Me

I enjoyed working at IBM: it was full of bright enthusiastic people who were mostly the same age as me. Some highlights were:

  • The early years with MPSX.
  • The STRUDL team.
  • Assignment in Boca Raton with the IBM PC division.
  • Managing the forecasting team at ASE.

But all good things come to an end: in 1996 IBM and I parted company and I started Decision Models with the objective of providing consultancy, software development and tools for decision support.

I have always been interested in pushing the boundaries of whatever software I am working with and so I was soon bumping up against the memory and performance limits of Excel. This led to the launch in 2001 of my website Decision Models. and FastExcel , my commercial product for profiling Excel calculation performance and memory useage. In the last 10 years FastExcel has been selling steadily and has been updated to run with each new version of (Windows) Excel.

My latest challenge is to learn C++ and start developing a new family of fast Excel functions to help minimise the slowdown caused by excessive use of Lookups, SUMPRODUCT and array formulae.

In 2009 Microsoft awarded me the honour of becoming a Microsoft Excel MVP. The best part of this award is getting to meet the Excel team and some of the legends of the Excel world at the annual MVP summit in Redmond.

My other passion is racing my Wayfarer dinghy TANJ3:


9 Responses to About Me

  1. Dear Charles,

    I am delighted to see you blogging. Though I had purchased Fast Excel about 7 years back, I still hadn’t used it as intended except for profiling workbook. I use it mainly for Name Manager. That is quite strange because I had purchased it to speed-up my Excel files. I haven’t yet made any assessment why it happened, but I will blame it on my reluctancy to read all the Fast Excel Help. But I am on my way to start using the Fast Excel stuff very soon. Hope to post my issues here as I always avoided contacting you via email for any help. Surely the stuff on this blog is going to be unique and top-class.

    CA Kanwaljit Singh Dhunna

  2. Excel beginner says:

    1-I wante to say thanks as you have helped me resolved my problem.
    2- Is it possible to add twitter account that I can follow your posting as RSS is not so funny in my opinion.

    Thanks and Regards

  3. Patrick says:

    Charles Williams

    Am looking for a UDF expert cum VBA/other programmer expert to help me come up with a Customised Desktop App. for several Functions, how they relate & special Reports


  4. Stu Davies says:

    Hi Charles & anyone else who may be able to help.

    Many thanks fro your great advice on excel performance, it’s been really helpful. I’m currently trying to use your ‘measuring calculation time’ macros that I found on your MSN blog on Excel Performance. Alas to no avail, I keep getting a calc time of zero on all tests. This as of 10.04.18 – anything you might be able to advise on that be very appreciated.

    Here is the url to your post: https://msdn.microsoft.com/en-us/vba/excel-vba/articles/excel-improving-calcuation-performance


  5. Vijay Verma says:

    Not sure how to contact you, hence trying to approach you from here. Of late, the first 4 lines in your MicroTimer is getting highlighted in Red in VBE (looks like some 64bit impact). Is there any remedy for this? (these 4 lines are)

    Private Declare Function getFrequency Lib “kernel32” _
    Alias “QueryPerformanceFrequency” (cyFrequency As Currency) As Long
    Private Declare Function getTickCount Lib “kernel32” _
    Alias “QueryPerformanceCounter” (cyTickCount As Currency) As Long

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