My thinking was, to take the current uptime and check it against a maximum uptime variable (initial input figure being 0), and if it is greater - then overwrite it.
I came up with something rough, which doesn't work. But I'm not sure on the best way to proceed now. This is the rough gubbins I came up with (my actual version is slightly diferent because I've split it over an inc file):
Now, I think the problem in my approach is that the highlighted item isn't returning the measured number, but instead the text MeasureUptime. How can I fix this? Or if there is a much better way of doing this, then please advise. I'm not very good with calc syntax, so I might be making some basic errors!
Of course, as you can gather, a key part of this is that the number has to be retained when the computer is reset/rainmeter is refreshed - therefore I thought WriteKey was the most appropriate route to take.