Hi Tom,
I’ve added some additional data to the bottom of your Calendar page which I hope will help. It’s not quite finished and I don’t think I’ve managed to do exactly what you wanted, I was more playing with the data and trying to manipulate it somewhat to get values out in different formats.
I’m running out of time this morning, but I hope something in there will help anyway. I may come back to it later.
The more I look it the more my brain starts to hurt!