Guys
First of all let me thank you all for your contributions.
With the confidence that it must be working I have tried again and Bingo, works as advertised
Now I promise you all, I have tried this facility at least four times before with four different MC revisions back dating to MC16 and never once did I manage to get MC to change my extended monitor refresh rate. I admit this is the first time I have tried it with .103, as I recall the last time was with ~.93
I can only assume each time I tried I either screwed up in some way (not sure there is much to screw up) or the particular versions I used had an issue.
I am now going to pass along the good news to my friends and hopefully we can all finally take advantage of this excellent facility.
Thanks again for the help, much appreciated.