Thank you, Paul.
I had been trying to use those options but they weren't working.
It turns out that the fields I was using had spaces put in them by timechart's default sep/format values so the dash options were silently failing.
Thanks to your link, I could copy the code in the provided examples, see it work and be able identify differences in the options in my own code and so to test field names.
Thank you! It was a big relief to work out what was going on.
