[Remind-Fans] Tracking N days after most recent event in a series

[Tim Chase]

I've got a situation where I have a couple different events that
aren't regular (they involve synchronizing schedules to get together
for lunch with friends)

What I'm hoping is to have something log-like of the form

  REM Feb 6 2023 MSG Lunch with Matt
  REM Mar 12 2023 MSG Lunch with Matt
  # when new lunchtime gets scheduled
  # insert the event here
  REM [magic] MSG Text Matt to schedule lunch

where the "magic" determines when the most recent event was and
adds some constant factor, say ~23 days to it.  I tried

  REM Feb 6 2023 MSG Lunch with Matt
  REM Mar 12 2023 MSG Lunch with Matt
  # when new lunchtime gets scheduled
  # insert the event here
  SET lastMattLunch $T
  REM [lastMattLunch + 23] MSG Text Matt to schedule lunch

but that doesn't do what I was hoping.  When I debug, that lastMattLunch
is getting set to 1989-12-31.

I think I understand roughly *why* (because that Mar 12 event doesn't
actually fire today since it's in the past, so the $T is unset/garbage),
so it feels like I need some sort of SCANFROM or IFTRIG, but I'm
not sure how that would look.

My hope is that there's some way to just add events without needing
to also update/duplicate the most recent event like

  REM Mar 12 2023 MSG Lunch with Matt
  REM [date(2023, 3, 12) + 23] MSG Text Matt to schedule lunch

and let remind(1) know what the most recent date was, even if it
hasn't been triggered because it was in the past.  It'd be less
painful if I only had one such thing to track, but the double-editing
becomes tedious with multiple such entries.

Any thoughts/ideas/suggestions?

Thanks!

-tim