What to do if your Excel is like mine
If your Excel is like mine, then it may run the simulations from this site very slowly even on a very fast computer due to what appears to be a bug. To avoid this, please follow strictly this procedure (better do not ask 'why' because I do not know -- I discovered this by chance, when I noticed a ten-fold speed increase in a simulation which always happened when I followed these three steps):
1) Exit Excel completely (close and exit all Excel files, close Excel).
2) Download the workbook which is attached further down, it is called "Start.xls", then start Excel again.
3) Open the downloaded workbook (called Start.xls). This workbook is meaningless, it has nothing in it apart from two rectangular forms, one of which is selected. Please DO NO CHANGE ANYTHING in Start.xls, just open it and keep it open the way it is. Do not deselect the shape, do not save it, do not edit it, do not do anything. Just keep it open!
Now, when you open a simulation workbook from this site, and only if you have a fast computer (like mine), Excel will run the simulation very fast. Press and hold the F9 key and you will see everything moving like on the screen of a real-time network analyser.
Why do you need to do the above?
You do not need to do the above if your Excel runs the simulations normally (meaning very fast indeed). Also, you do not need to do it if you have a slow computer, it will run the simulations slowly no matter what.
But if you have a fast computer, which inexplicably runs very slowly the simulations downloaded from this site, then after you do the above, Excel may become alright. You can tell when your Excel has the same problem as my Excel, if you look at the pictures in a simulation: if they do not display correctly or they display only the text or if they change very slowly -- then you have the same problem with your Excel like I have. Do the above and your Excel may start running fast and displaying the pictures normally (they will appear like video clips, but they all are actual, real-time, graphs of the simulated signals).
See the workbook attached (it contains no macros).