This should work - at least if you're not staying connected for more than 1 sunday smile
Just to play safe, and to reduce the (unnoticeable, just cosmetical) overhead of checking every minute, you could do something like:

Code:
on *:start: midnight.check

; offline timer that triggers once at midnight
alias midnight.check { timermidnight -o 0:00 1 0 midnight }

alias midnight { 
  if ($day == sunday) { <yourcommand(s)> }
  ; timer to restart the main timer at 0:01 (so it won't re-fire as it's still 0:00)
  timer -o 1 60 midnight.check
}


Edit: Just to add to Riamus2, note that a timer like "timerX 0:00 0 0 <stuff>" would "spam" in a loop, thus the above construct.